Fuel problems
 

Hi, I have 1995 Suburban 1500
It has the 6.5L Turbo Diesel.
Full tank of fuel.

Yesterday driving down the road it acted like it was running out of fuel.
Stalled and towed home.
No fuel at injectors.
The lift pump only works if I jumper the lugs in the board where the relay plugs in.
It pumps fuel to the filter and out the little drain on the top.

The relay is new the fuel is clean.

I'm leaving the jumper in the board to keep the lift pump working.

What else is operated from this relay?
Would it hurt to leave the jumper in place?
Or could I put in a switch and operate it when running?
Should the lift pump shut off when it reaches a certain pressure?
Is there a fuel pump pressure switch in this system for the lift pump?

Any help would be appreciated.

I read the 4th post about the lift pump and circuts problem.
It's kinda like mine.

How would you check the injector pump or that system.

I'm a marine mechanic and have tools just not the knowledge on diesels.

Thanks

MORE INFO,

I've jumped the lift pump and the filter is full and the drain has lots of fuel coming out.

I turn the key and it runs for a second then dies.
The injectors have fuel leaking out when I loosen the cap nut as I turn it over.(I bled the lines)

Sounds like a sensor or pressure switch or something not allowing the motor to run??

Sounds like the OPS (oil pressure switch) use only A/CDelco parts store ops are junk.

Seems to be FIXED!!!
Replaced the ops and it's running!!
When I bought the truck a year ago.
The guy said to look out for that problem.
He even included a new one and a socket.

I replaced it and it ran for a short time.
Then stalled again.
I'm guessing it was the wrong sender??
Or a cheapo. It was from Auto Zone.
The new is from Napa.

THANKS for all the help.

I repair boats and motors , if anyone needs any help?? ASK

You may want to go to the dealership and pick one up and have a spare I got one they are less than $30 and Google ops mod for the 6.5 I have the stuff to do it but have yet to get my lazy butt around to doing it.

Did it again??

Put in a new ops.
Runs!!
Why would it go bad so soon?

Something in the system to make it do that?

Is there any way to jump the plug the next time it goes?

I'm gonna carry a new one now.

The place the switch was plugged in was way deep down in the back of the motor.
Would it hurt to extend the brass tubing to make it easier to get to??

Did you put a A/CDelco in this time ? If not you should have. Parts store brands are inferior to original equipment I know they look the same but they aren't.

And look here there is a ops mod that you can do to prevent this from happening do not drive around with the lp jumped if you have an wreck and a fire you will feed the fire until the battery is dead.

The Not sure where the ops was bought that was on the truck???
Very possible A.Z. or Advance.
There was a new one(a.z.) along with a socket in the glove box.
The PO told me about them going bad.
I replaced the original a while back.
I used the one in the glove box (from A.Z.)
It worked for a week but was giving me the wrong reading on the OP gauge.
It went bad after about a week.
Replaced it with one from Napa.
That lasted less than 1 day.
Had to get another from Napa as the dealer was closed.
I bought a spare from O'Reilly's .
Gonna buy 2 from GM dealer on Monday.
The dealer is 25mi from me and at the time I had no way of getting their parts.
The place that might carry the OEM parts is on vacation. :(
Then take back all three of the bad and good cheapo's

I bought 1/4in brass tubing 4 pieces and made an L shaped extension.
I had/have a high pressure hose I could have used but thought the OPS might need a ground???
Doesn't leak and it seems to be about the same as what's on other 6.5's

Your issues is not with the OPS. Your PMD is bad. The truck will idle without a working lift pump. The injection pump will suck fuel past a dead lift pump but will not get full flow. You can verify by adding your jumper to the relay to supply power to the lift pump bypassing the OPS all together. If the truck still dies this will confirm your PMD is bad. The PMD is known for working when cold, but after it heats up it will randomly die. I have been through this before. Some days it would run for 2hr and other days 2min. If you haven't done the PMD relocation kit yet, I would strongly recommend it.


The OPS is dual purpose.

1st mode is lift pump relay (ORN +12v input) -> (GRY +12v output to the lift pump). ***Only when there is oil pressure

2nd mode is oil pressure sensor (motor ground at threads) -> (TAN ~5v output to dash)

By modifying the ground you can/will get a offset in the reading of oil pressure at the dash. As long as you only use brass elbows, you shouldn't see any issues. If you want to run a rubber hose you will need to add a ground from the block to the threads of your OPS. To help increase the life of the pump you can add the lift pump relay mod to remove the load of the pump from this sensor.


https://cimg5.ibsrv.net/gimg/www.die...714bc6c5ce.png

I've been afraid to go far!!
It died again today.
Tried a different PMD and it made no difference.

Changed to the spare(new) OPS and it started right up?????

Ordered the harness and relay from Leroy Diesel.

Should get here Mon/Tue.
Sure hope this helps?


Now would there be a problem in the injector pump making it do this?
Someone said there is a pump in there and it should draw fuel and run, poorly but run.

I have a spare injector pump. How hard is it to rebuild it?

Another question: I pulled a boat out of the water today.25ft.twin motors fly bridge, cabin.
Basically I'm saying not a small boat.
It doesn't seem to have the OOOMPF it should.
Almost struggled to pull. But the tires broke free and spun.
It got it out but my Ford V-10 would pull the Burb backwards.

I never had a diesel and it seems like it's kinda lazy with the response??
Or maybe it's my imagination?

Gonna drive my son-inlaw's truck(Ford Diesel) this afternoon and see how it handles

Relocating the PMD is a must and having a spare PMD is a must, and while you do the relocate you should take all engine grounds apart and clean them especially the one one on the rear passenger side cylinder head( poor grounds are know for all sorts of gremlins) and what ever you do don't use reverse to pull anything of significant weight if you have the 480LE automatic transmission they use second gear for reverse gear, and I have had 12-14K lbs behind my 6.5's before I've had both the NV4500,480LE transmissions they did it but there is no comparison to the Duramax,Cummins,Power-stroke mostly the 6.5 is known for fuel mileage, I hope you get it figured out good luck.

Mayhem

PMD is under the front bumper.
My spare PMD is good.
The grounds were redone when I replaced the pass side head.
Yes a 480LE is the trans.

It pulls just not like I thought it would???:tu:

Went for a quick ride.
The truck ran great until I looked for a parking place.
It was like turning off the key.
Usually it kinda acts like it's ran/running out of fuel.
Not today: I had a new GM OPS and put it in.
Nothing!!
I had bought the kit from Leroy and installed it.
Along with a New Bosch OPS.
Again Nothing!!

I have another PMD and while it was running I change them out.
It ran with both. So I think the PMD is ok.
After it stopped I changed the PMD and nothing.

Is there a low oil sensor in this motor?

It doesn't have any warning lights.
I ran the codes and got 1 2 1 2 1 2 and 1 2 again.
I understand the codes are 1/2 1/2 1/2 and if no others are there it flashes 1/2 again.


Any ideas?

When I had my 94 now that I think about it it did the same thing turned out that the CPS (crankshaft position sensor) was bad this is another one of them you need a A/C Delco parts hopefully if you replace yours it comes out easier than mine did its down by the oil pan on the driver side of the block.

It throws 2 codes 29 and 49
The warning light doesn't come on unless the jumper is installed when I put it in to read the codes.
It's like something shuts off when it gets hot?

It's not overheating.
New radiator, clutch fan.:td:

I did a code scan again. 29/36/49/57/62/91????
I search the motor for loose wires and questionable grounds!!!
I found some but not positive they were actually loose. Maybe ???
I removed and replaced the connectors anyway.
Tried to start and nothing.
Then from the diagnostic tests the first thing I did was disconnect the optical sensor and tried to start it.
Started right up.
Plugged the sensor back in and it still runs????
I deleted the codes.
Started and let it run, shut down, started again.

Did another code check.
Found 12/12/12????
Not positive the problem is fixed but how can you tell if there is a problem if it runs and doesn't show codes??

Anyone want to buy a burb? :)

I repaired or redid the grounds??? Still wouldn't start.
Tried starting with the replacement OSF no start.
Took it out and it started.
Let it idle for 45min.
Took it for a short ride yesterday 1-2mi. NP
Again today 5 mi. NP
Recap: Tank full and clean, LP working as it should.
Stalled and I changed the OPS started and ran a short while.
Did that again, changed and started , ran for a short while.
Installed the relay and harness from Leroy's Diesel. No difference.
Used AC Delco OPS. and a Borg Warner. No difference.
When it was cool it would start. Then shut down when warm(not overheating).
Then changed the OSF and still nothing??
Took it out and left it out and it runs!!!
I also tried a second PMD mounted under the front bumper.
The old wouldn't come off so I drilled and tapped holes next to the old to supply a good mount.
Now I have 2 mounted in case one goes bad.
Hopefully this will run for another year??

Changed the OSF and no difference, removed it and it starts. :jump:

Are you saying optical sensor? (OSF)?

Optical sensor filter.

Okay it's not often when the optical sensor fails but they are pricey you may just want to pony up and replace the IP as they only have so much life in them to begin with but if you decide to replace just the sensor I found this.

Roy Halvorsen

That's a good link.
I have a 2nd IP, it's used.
I'm fairly good with tools could I rebuild it?
Or do I need to send it away?
My PMD(Halvorson called it a FSD) is mounted on a heat sink under the front bumper.
In a previous post I had mounted a second one next to the original.
So now I have 2 good PMD's

Thanks for the link and any help.

I think you may be better off sending it to be rebuilt the way I understand it there are tolerances of 1000th of a inch involved.

Do you want to sell it?

After I removed the radio filter in the harness it's running like new.

It gets good mileage and is dependable again.
Any gasser burb wouldn't get anywhere near the economy I get.

I think I'll keep it.

Unless I get a good offer?:jump:

Did you ever check the lift pump flow?

Yes I did.
Someone on one of the sites I was talking too gave me some specs on flow and amount I should be getting.
The pump is operating like it should.

Since I removed the audio filter it's been running great.

I installed the bypass from Leroys Diesel.
Not sure if that helped or I just spent 150$ ??

It's back to running like it should.
Thanks for asking.

You having trouble?