Caterpillar 268b no crank after bad fuel pump and or filter. Now power to engine start relay with switch turn. Can jumper wire at relay.

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CATT0268BPLBA0114 serial number

Problem began: dirty filters. Cutting out at high rpm. Would change and it would run perfect for a longtime. Duration got shorter between filter changes. Would dump out filter and it would appear dark brown dirt fuel.
Then, a little worse with a clean filter.
I then tested fuel pump separate from machine with 12v battery and hose into bucket. No pressure.

I ordered pump.

In meantime, I needed to move machine. Hooked up pump and tried to crank it.
Crank would not happen. No power to relay switch wire.
Now, I assume the start relay is the 2 relays on the left (drivers side if it's a car) by the circuit breaker. One must be the glow plug relay (cold start) and other must be just crank starter. Right?

The trigger wire on the starter is thick white.

Engine turns over fine as normal if I jumper wire.

I noticed on the dash that the battery light is on when switch is in on position.
Also, when switch is on position the oil pressure light is on. This has happened lots of times but when engine is rubbing oil pressure light is off.
No knocking. Engine smooth as butter.

I replace battery.

Cleaned ground to bell housing too.

In past, I had a leaky oil pressure sending unit. I check oil pressure sending unit and the wire to it is jangly.
I need to replace.
*****As a side note or question....is the wire to sending unit alway ground (negative) and if it grounds out internally the sensors knows it has low pressure? While I'm waiting on a new one in mail...would I just run a jumper wire to ground?

I touched the wire to positive power a brief second and light went out on dash. Odd. But this was AFTER all of these problems. After unhooking and re hooking battery terminals the light cams back on.

Back to issue.

I've raised cab. Looked through all wiring harnesses. Looks good.
I've babied this machine. Bought new. Careful. I always watch all hose and wire rubs.

Ignition switch sounds normal clicks.
If I need to go in to the ignition switch, I'm confused about the best way to remove switch panel on upper left cab corner. I don't wanna break any plastics. I've looked on this forum and found a post, but the answers seem undecided.
I've cleaned ground from cab to frame behind seat when cab is raised.

I have no computer scanner. Do I need one?

I have been told the switch wire goes through one of the ecm and the ecm sends power to start relay. Does it need reset? How? Battery cable remove?

I have jumper wired or checked seat sensors, arm bar switch, door switch.


I do not have a service manual for this machine. Not sure which latest version to buy on eBay etc?

Lastly, I don't see how this fuel pump
Issue occurred at the same time as this wiring issue? Odd.

On a Facebook forum, a guy sent me a schematic of a b series machine. It was NOT specific to mine.
Wiring didn't get in to my switch wire etc.

I could *NOT* print what he sent me. When I print it is blurry.
I've tried to screen shot sections of wiring diagram and it IS blurry. Is it scrambled for security?

Can Anyone send me a clear, printable clear wiring diagram to whole machine that is clear and printable?

Thanks so much for any advice and documents sent.

Sorry the post was so long.

 

[Nige]

First up kudos for posting a Serial Number. You would be amazed at the number of posters who don't.....

There is a bit of a problem though, it's missing a digit at the end. There should be 5 digits after the "LBA", you only have 4. It will be important because there are differences in things such as fuel lines depending on Serial Number.

A lot to digest but here are a few suggestions.

Fuel issues. IMO you should start by cleaning out the tank. Everything that's landing in the filter is coming from there. It could be something related to a micro-organism in the fuel that will require a biocide to eliminate.

When replacing filters on a system as contaminated as this one obviously is, the head of the fuel filter/water separator needs to be removed and all the passages blown out to ensure they are not plugged with fine debris.

Need to check the electrical supply to the fuel pump. Fuses, wiring, etc.

 

[Nige]

Electrical issues I can send you a schematic that applies for all LBA-prefix machines. Keep an eye on your message inbox.

You can use that to trace your lack of power for starting.

 

[Nige]

Now on to the subject of manuals. There are 3 different manuals for this machine.

1. Operation & Maintenance. SEBU7731. The slim one that fits in the seat pocket. Covers operation & basic maintenance tasks, lubricant specs, etc, etc.
2. Parts. SEBP3928. Does exactly what it says on the tin.
3. Service. RENR8740. Price new $740. A complete guide to repair, specifications, troubleshooting & diganostics. This manual when new will also contain SEBU7731. Sometimes in used paper manuals the O&M section will go walkabout.

You could search the usual internet marketplaces using the Cat Publication references above and see what pops up. Just be aware that a lot of sellers have a very high opinion of what they are selling, so much so that they ask higher than new prices.

 

[Nige]

I have no computer scanner. Do I need one?

I would not say so at this point. If it comes to needing to read Diagnostic Codes it ought to be possible to locate a local independent tech who has Caterpillar ET diagnostic software and can scan the machine for you. I would park the idea for now.

 

[bill fold]

I would not say so at this point. If it comes to needing to read Diagnostic Codes it ought to be possible to locate a local independent tech who has Caterpillar ET diagnostic software and can scan the machine for you. I would park the idea for now.

NIGE, you are always the biggest help on here. Thanks. - could I possible go to a professional print shop and give them the file/link of this wiring diagram and have them print it in a clear and legible manner on a proper large scale big piece of paper? Whatever the fold out size is? One thing that would be cool for me to keep in my shop is a piece of white plastic board about the size of half of a plywood with this wiring diagram printed on it!!

 

[bill fold]

Electrical issues I can send you a schematic that applies for all LBA-prefix machines. Keep an eye on your message inbox.

You can use that to trace your lack of power for starting.

I have searched high and low all over my machine and for the life of me I cannot find the issue. I'm worried I'm gonna have to remove the top steel cover of the cab to get to the star bit internal screws of the overhead dash panel. Oh my! I don't want to bust my plastic panel. Dang it.

One thing I forgot to mention. After I diagnosed my pump issue, I went to start it, and it would not start. I thought battery was dead. I put on jumper box.
Then when to clean cables and the positive wire to the starter from battery broke off. It had been barely getting connection as if it had been wiggled too many times. Like wiggling wire till it breaks (so to speak).

I removed wire. For a terminal eyelet and soldered it on the end of wire. Reinstalled it after cleaning starter hot post connection.

Could this low voltage at a weak joint damaged something in ECM?

So, with new batter and nice clean wire and connection, I can jumper wire starter relay but NO trigger to relay. I turn ignition switch to on....everything normal. I click to start...(fuel pump starts running but starter does not engage). I guess fuel pump never begins until start is activated, right? As I type this, I begin to wonder...maybe power goes by the fuel pump first before to the start relay. I've got to zero in on this wiring diagram. I'm not so good at tracing the wire path via the diagram. If anyone can mentally and visually follow What I've written, maybe they can offer some suggestions.

Basically, the switch must be doing something if the fuel pump activates in the start position of switch.

Thanks everyone.

 

[Nige]

The electric fuel pump is used to prime the system after a filter change. If you turn the key to the ON position and leave it there the pump should run for 30 seconds or so, basically long enough to fill the filter, then stop.

could I possible go to a professional print shop and give them the file/link of this wiring diagram and have them print it in a clear and legible manner on a proper large scale big piece of paper? Whatever the fold out size is?

Certainly you could. IIRC the size when printed is somewhere around 40” x 30”.

 

[bill fold]

The electric fuel pump is used to prime the system after a filter change. If you turn the key to the ON position and leave it there the pump should run for 30 seconds or so, basically long enough to fill the filter, then stop.

Certainly you could. IIRC the size when printed is somewhere around 40” x 30”.

Still working on this thing. I'm thinking so far that it must be the switch or ecm not telling start solenoid to trigger.

I'm trying to figure out the best approach to removing the upper left hand ignition switch plastic overhead panel. Not sure if I should lift the steel roof of the cab or what as it seems there is no way to access the star bit screws. I certainly don't want a busted plastic switch and instrument panel.

I'm perplexed as to why the electric fuel pump comes on ONLY when I click over to "start". And it never cuts off until I turn switch to off.

So, the plastic electric pump only primes the filter, doesn't pump fuel as it's running to the injector pump?

The injector pump must have a lift pump built in.

All over my machine my wiring looks perfect. No chaffing.

Thanks

 

[Simon C]

I have opened up one of those plastic overhead panels two times. Was very ignorant is all that I can recall. I believe I repaced a couple torque screws with hex head bolts to make life easy. I remember they were hard. You have to open up left side to get at parkbrake switch on 236b machines.
All the best to you.
Simon C

 

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Still working on this thing after all this time. So far, all wiring harnesses look good. Can't see a cut or worn place in fiber loom wrap.

Removed the crazy plastic overhead dash. That is insane engineering.

Wires perfect.
New key start switch.
New parking brake switch.

Removed floor board.
Cleaned debris from floor board.
Connection at left hand side interlock ecm looks good as well as right hand side ecm for all else.

Cleaned grounds.

Took interlock ecm (on left side kf sitting in seat out.
Used star bit and remove face to see backside of circuit board.
No black spots. Looks clean and tidy and sealed and brand new.
Put back together.

Tried to test white wire from start relay back to ecm. No connection. Not sure I'm doing that right. And ideas?

Just for fun, I used alligator claw test wire/jumper from hot wire on start switch over to start wire. I hear a click inside the hvac box??? I put my ear to it and click like strkng solenoid click.
But...the fan motor turns fine and with power it spins fine.
I do have a corroded fan motor speed rocker switch that i have to click back and forth often as it has corrosion on backside plug (dust and rain from window crevice {bad b series cab design}).

Again, I can jumper wire start solenoid and get engine to crank over just fine.
Starter sounds good.

New battery.

Battery light on dash still on.

When this problem began, to recap....a month ago, seemed like battery dead. Jumped it off. Perfect a month after that. But battery light on dash. Then filter getting dirty quick.
Run perfect with change.
Then finally, seemed to have dirty filter at high rpm and I backed it up to change it.

Then would not crank back.
Fuel primer pump wouldn't come on.
Tested it independently with independent 12v source. and not much hum. Intermittent. And no pump.
Ordered new one. Installed.

No crank.

Then noticed positive wire to starter fell off. Had been hanging by a thread where it has a bend in end eyelet plug of wire. Soldered a new one on. New battery. Still no crank.

Fuel shut off solenoid does click when hand feel on it.

When I turn key to "on", priming pump does not rub. When I turn it to start, pump runs and does NOT cut off.

I'm thinking the priming pump kept running while engine was running causing aeration at high rpm until pump was damaged.

But why the cross over in power to start switch. Cannot find raw wire insulation causing shorting between start wire and fuel priming pump.

Checked all relays with tester.

What tells the priming pump to run 30 seconds and then turn off? A timer? Ecm?

Now, battery died on its on. New battery. Went to charge it, won't charge. Remove battery, charges fine and load tested good. I must have a dead short to frame.

Some thoughts: alternator has a bad diode, regulator, or internal part? Indicated by battery light in dash? Ecm sees this and will it not allow to start?

Starter works but maybe a wire from burrs touching case?

Original starter and original alternator.

Can I remove my ecm's and take to cat dealer and gave them test them to rule then out as possible issue?


I'm sorry I was all over the map with this message. Maybe someone can decipher. Thanks

 

[bill fold]

Additional update. Just for archive to this issue in case someone else encounters this.

I took my alternator off and took to a former alternator starter shop rebuilder guy who closed down and moved his shop to his home shop. He took my Denso alternator apart and he couldn't even get the backside part off of it it as it was corroded and the little bolts and nuts were seized and had rust from dirt. He tried to cut rick groove the nuts or the little bolt heads and he got it down to one he couldn't groove to remove with flat base. Someone broke in the process. He said that this "might" be my issue and it's intermittently (I think he says) grounding out, overcharging, or under or working perfect. This alternator is the original. I asked him if the ecm would show this as a fault or whatever as the battery light is on the dash. He said "it's possible" if there how the ecm works. It would explain the battery light at least. I told him I had a positive terminal main battery wire going to starter that was hanging rather at starter bolt eyelet and it fell off when I went to digging in to this. He said anything is possible with an alternator like this. He said the little springs on the things inside were sticky, I'm assuming the part that controls the brushes floating in and out, forgot the name.

So, he says..just order a new one. You need it anyway. He recommended dbelectrical.com - I ordered it. Waiting.

So, is this doesn't work, I needed an alternator for anyways.
battery is new.
Starter key switch is new.
Fuel primer pump is new.
Park brake switch is new.

Wiring looks perfect.
At this point I'm starting to look toward ecm interlock failure? Maybe alternator did it?

Can I remove the ecm and take to cat dealer and get it tested?

Should I send mine off and have repaired with program staying with it? Buy cat dealer ecm and maybe they sell it preprogrammed?

Also, should I get a cat code scanner?
I also have a cat 320c. Maybe it'd pay me to own a scanner. Or a simple scanner that helps me diy repairs. Not sure what kind? Where or price?

Thanks for anyone who replies.

 

[Nige]

Also, should I get a cat code scanner?
I also have a cat 320c. Maybe it'd pay me to own a scanner. Or a simple scanner that helps me diy repairs. Not sure what kind? Where or price?

Can I remove the ecm and take to cat dealer and get it tested?

Same answer applies to both questions.
The Interlock ECM is "hard programmed" and is not accessible with any type of scanner as far as I am aware. Happy to be corrected if someone else knows different. The only ECM that a scanner will detect on your machine is the AUX Hydraulic ECM.

At this point I'm starting to look toward ecm interlock failure? Maybe alternator did it?

It's possible. Post a photo of the Interlock ECM and especially the electrical connectors from the machine wiring harness to said ECM.
Also try unbolting the ECM from its mounting and take a good look at both the electrical connections and also the back side of the case for hidden corrosion.

Should I send mine off and have repaired with program staying with it? Buy cat dealer ecm and maybe they sell it preprogrammed?

Similar to the answer above. The Interlock ECM comes already programmed. I haven't heard of anyone successfuly having had an Interlock ECM repaired if it has suffered an attack by corrosion. The usual solution is a Reman ECM. If you go to Cat to ask for a price make sure you are sitting down when they tell you. Last price I heard was North of $3k for a Reman one, a new one was even more expensive.

This company sorted an Interlock ECM for at least one other HEF member. One was on a 226B so it will be the same Part Number as yours - 154-4233. He sent his old one (badly corroded) to them for evaluation. They declared it to be non-repairable and offered him a Reman unit. The first one they shipped did not work right but they swapped it no questions asked for a second unit which worked fine. I have never dealt with them personally.

 

[Vetech63]

could I possible go to a professional print shop and give them the file/link of this wiring diagram and have them print it in a clear and legible manner on a proper large scale big piece of paper?

I do this with prints all the time. Take it to a print shop and have them enlarge it to a 24" X 36" in color.

 

[Nige]

Have you checked whether or not three wires at the Interlock Control ECM have power when the key switch is moved to various positions.?

First. Do you have power.? When the key switch is moved from the OFF to the ON position wire 126-A84 PK on Pin 1 should energize.
While you are in there check that wire 201-A2 BK on Pin 3 has a good connection to ground.



At the other end of the Interlock ECM connector wire 307-A67 OR on Pin 62 should energize when the key switch is moved from the ON to the START position. It should be de-energized with the key switch in either the OFF or the RUN position.

At the same time as 307-A67 OR energizes (key switch moved from ON to START in other words), wire 306-A11 GN on Pin 64 should also energize.

Test all the above and report your findings.

 

[bill fold]

Have you checked whether or not three wires at the Interlock Control ECM have power when the key switch is moved to various positions.?

First. Do you have power.? When the key switch is moved from the OFF to the ON position wire 126-A84 PK on Pin 1 should energize.
While you are in there check that wire 201-A2 BK on Pin 3 has a good connection to ground.

View attachment 325868

At the other end of the Interlock ECM connector wire 307-A67 OR on Pin 62 should energize when the key switch is moved from the ON to the START position. It should be de-energized with the key switch in either the OFF or the RUN position.

At the same time as 307-A67 OR energizes (key switch moved from ON to START in other words), wire 306-A11 GN on Pin 64 should also energize.

Test all the above and report your findings.

View attachment 325866

You are the monster helper on here. Thanks so much so far.

Ok. Everting you say listed above works when checking pins at ecm harness except in the end #64 does NOT energize.

64 does NOT.

Also, on black on number 3 I couldn't figure out exactly how to test that as ground. Jumper wire or use a multi meter in some way?

So 64 is NOT sending power through orange wire to the start solenoid? Is it orange all the way to start solenoid?

Seems like my fuel priming pump has an orange wire and my start solenoid trigger wire has a white wire? I may be wrong. It's all running together as a blur in my mind now.

While i was slow to reply to my own message, i had alternator and starter tested and alternator looked crusty inside and I ordered one and replaced prior to this test. Once doing that I blew a switch fuse in fuse panel. Not sure why. First time that ever happened in this massive research repair.

And just to clarify, the fuel priming pump should only turn on when key is in ON position and not start position. Correct? Mine runs once I clock start and stays on. No 30 second cut off.

As I tested these pins it was of course with ecm pin harness unplugged. If power can get to orange 64 wire without ecm why even have the ecm? Am I just answering future question that 64 should not be getting power unless plugged back up to ecm? Uh oh.....

By the way...I removed ecm and cleaned grounds and took apart. I didn't pull green circuit board away from pin panel on inside but it looked bone dry and perfect.


Any help appreciated.

 

[bill fold]

You are the monster helper on here. Thanks so much so far.

Ok. Everting you say listed above works when checking pins at ecm harness except in the end #64 does NOT energize.

64 does NOT.

Also, on black on number 3 I couldn't figure out exactly how to test that as ground. Jumper wire or use a multi meter in some way?

So 64 is NOT sending power through orange wire to the start solenoid? Is it orange all the way to start solenoid?

Seems like my fuel priming pump has an orange wire and my start solenoid trigger wire has a white wire? I may be wrong. It's all running together as a blur in my mind now.

While i was slow to reply to my own message, i had alternator and starter tested and alternator looked crusty inside and I ordered one and replaced prior to this test. Once doing that I blew a switch fuse in fuse panel. Not sure why. First time that ever happened in this massive research repair.

And just to clarify, the fuel priming pump should only turn on when key is in ON position and not start position. Correct? Mine runs once I clock start and stays on. No 30 second cut off.

As I tested these pins it was of course with ecm pin harness unplugged. If power can get to orange 64 wire without ecm why even have the ecm? Am I just answering future question that 64 should not be getting power unless plugged back up to ecm? Uh oh.....

By the way...I removed ecm and cleaned grounds and took apart. I didn't pull green circuit board away from pin panel on inside but it looked bone dry and perfect.


Any help appreciated.

Update to my update. I put the pin connector back on the ecm and put test light sharp probe into the orange #64 start relay backside and when turn switch to start I go a test light light. Confirming ecm is sending power to orange wire 64. Now I must have a loss somewhere between ecm start relay. Wires and harness look perfect all the way with no rubs. Grrrrrr this is troublesome!

Thanks guys

 

[bill fold]

Update to my update. I put the pin connector back on the ecm and put test light sharp probe into the orange #64 start relay backside and when turn switch to start I go a test light light. Confirming ecm is sending power to orange wire 64. Now I must have a loss somewhere between ecm start relay. Wires and harness look perfect all the way with no rubs. Grrrrrr this is troublesome!

Thanks

To double check I put 2 test lights on wire 64 and 62 to see if both energize and de-energized when clicking to start. They both do.

Wires and harness look perfect all the way with no rubs. It of course I cannot see inside the military braided loom.

Another concern i am having is the brand new ignition switch metal housing has a little bit of spark to it if it touches metal. I don't have it secured to the plastic dash yet and the windows glass is out of the side and if it dangles over against roll cage it sparks. That is leading me to wonder if i have power to a ground somewhere going to switch??

Can there be an oddity such as a bad dash indicator circuit board or glow plug wiring harness strip along top of cylinder head. I have never ever needed to use the cold start function. Ever. Always cranks on first touch of starter.




Thanks guys

 

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