Engine Died, Cranks but No Start

[utah smitty]

Hi


I know engine starting problems have been discussed in many other threads, but I've not had all my questions answered.


I have a 1995 6.5TD with 138,000 miles on it. It has a new inj pump, rebuilt heads, injectors checked for flow. PMD has been relocated to behind the bumper; updated cooling system w/Duramax fan.



I had just finished mounting my backup camera and went to drive it and check backing in to my trailer on the other side of the property when it chugged once then stalled. The engine cranks, but it won't start.



When I bought it, the owner said it occasionally would stall and he thought the lift pump might need to be replaced. I had already done some research and figured the lift pump wouldn't be that big of a deal, so I bought it.


I've put approx. 1,500 miles on it since I bought it, including towing a trailer with a side by side from the house to our recreational property 125 miles away and back. There's been twice that it cut out, very briefly, then ran fine. The first time I attributed it to the rather touchy accelerator pedal when I needed to downshift. The second time was only like a short cough. I have noticed that it seems to not have as much power as usual, but we've had some really hot weather here and I thought that might contribute to it.


So, I've checked all the fuses and they're good. I let it sit overnight and tried to start it this morning... same thing...cranks but doesn't fire. I can't tell if the lift pump is running or not. I turned the key on and took the fuel cap off but couldn't hear anything.


What should I check next?


Regards,


Smitty

[Robyn]

How old is the PMD ???

Basics apply.

Check to be sure that the fuel shut off solenoid is working (Round item on top of the IP ) Have a helper turn the key on and off and listen/feel the shut off to see if it is CLICKING

Check for fuel flow to the IP.

On a 1995 it is easy.

With the transmission in D (Engine off) turn the key to the start position.....lift pump should run and you should hear it making noise.

Disconnect the fuel inlet to the IP and stick it in a can or suitable container.

Turn the key to start with tranny in drive position (ENGINE OFF, PARK BRAKE APPLIED)

Fuel should flow from the hose into the can.

If fuel flow is good.......PMD IS A PRIME SUSPECT......Even if it is fairly new.

The PMD can fail after very little mileage......
What brand of PMD ????

I have had the best luck with FLIGHT SYSTEMS brand PMD

Check things and keep us in the loop.

[a5150nut]

Lift pump is inside frame under your feet sitting in drivers seat. Look under the truck, listening in the tank wont do any good.


Robyn gave you very good standard trouble shooting for 6.5s. She knows these trucks inside out.

[utah smitty]

Thanks for the input, Robyn


My truck has the NV4500 Manual Tranny, so I can rule out a neutral safety switch.


I'm still a little fuzzy as to what components can stop the fuel flow to the filter. If I understand correctly from your post, if the fuel is flowing to the pump, but the PMD is not working then the engine still won't fire, is that correct?

Late last night I read from another source that the 94 and 95 6.5 Diesels wouldn't turn on the lift pump and pump fuel unless the engine was cranking over, so this morning I had a friend help me. I attached a hose to the small nipple on the cap on top of the fuel filter housing, opened the cap a little, and had him crank the engine. I actually heard a rattle for a moment when he first turned the key on and before the engine cranked, but no fuel came out of the filter housing. I had him turn the key off, wait about a minute, then turn the key to on... no rattle this time. When he cranked it, again no fuel.

I assume that the pump is working but something is preventing it from getting to the filter. Would the Oil Pressure switch do that?

I'm not sure if the PO has put in a Oil Pressure Switch bypass. The truck is parked with the driver's side against the curb and I'm too big and too old to crawl under the truck and look at the pump.I guess I'll have to get it towed to my shop and put it on my lift before I can get under it.

I'm going to buy a PMD just so I'll have one regardless if this one works or not. Is there anything else I should look at buying?

Thanks,


Smitty

[utah smitty]

Okay, so here are some pictures of the PMD, and the harness to what I think is the glow plug relay. The PMD is mounted directly behind the license plate on the front bumper. It's a Stanadyne...is it the newer grey model? You can make out the part number (33405) on one of the pictures.

I have to say that if I have to change out a PMD on a lonely road at night, or during a snowstorm, etc. that this would not be a good place to mount it. I'm seriously considering mounting it somewhere more convenient.... any suggestions?

Another picture shows the top of what I think is the glowplug relay. Interestingly, there is a heavy gauge orange wire that was cut off, and the wire from the relay connected to what looks to be a white or gray colored wire. I don't know if the original circuit was defective, or if some modification was made.

I can't see any indication that a relay was installed for the lift pump. I'm petty sure the two rectangular metal boxes (one with 2 red wires, the other with a red and black wire) mounted above the brake master cylinder are circuit breakers. Both connect directly to the 12 volt lugs at the back of the fuze box. One of the red wires for the one on the right leads back to the rear and is 12 V auxiliary power that was wired to the trailer electrical socket. I disconnected it from the fuze block because I didn't want to have it supplying 12 v power continuously and possibly draining my batteries. I believe the one on the left with the black wire also leads to the rear, but I'm not sure what it attaches to.

Anyway, I'm trying to discern what i actually have here, and since the original owner is no longer alive I'm having to make educated guesses. Any input would be appreciated.


Smitty

[Robyn]

If no fuel is coming out of the filter when cranking the engine and the pump is not making any noise (The lift pump makes a noticeable noise)

Either the lift pump is bad or there is an issue with the electrical circuit to the lift pump.

Get that sorted out before fooling with the PMD

This could be an ignition switch issue......power flows from the 12V feed to the lift pump as long as the starter is engaged.

Easy thing is to get the rig so you can access the Lift pump and then check power to the pump.

A simple plug in is used down there...

Once the engine starts and oil pressure is present the power transfers to a feed through the oil pressure switch.

These can and do fail.....but you still need power feeding to the lift pump during cranking......


Could be as simple as a bad lift pump.....these too fail over time....

[utah smitty]

If no fuel is coming out of the filter when cranking the engine and the pump is not making any noise (The lift pump makes a noticeable noise)

Either the lift pump is bad or there is an issue with the electrical circuit to the lift pump.

Get that sorted out before fooling with the PMD

This could be an ignition switch issue......power flows from the 12V feed to the lift pump as long as the starter is engaged.

Easy thing is to get the rig so you can access the Lift pump and then check power to the pump.

A simple plug in is used down there...

Once the engine starts and oil pressure is present the power transfers to a feed through the oil pressure switch.

These can and do fail.....but you still need power feeding to the lift pump during cranking......


Could be as simple as a bad lift pump.....these too fail over time....

Thanks, Robyn.



So, if I understand it, I should find voltage at the lift pump when the starter is engaged...if not, then probably a bad ignition switch or oil pressure switch. If it does have voltage, but no sound from the lift pump when cranking, then the lift pump is defective.



I've seen listings for a wiring harness that uses the OPS to trigger a relay rather than pass all the current through it's relatively thin wire. The harness also provides heavier gage wire for the lift pump and oil pressure switch, etc. to increases their reliability. Is this a good thing to get?



On a related note, while looking to purchase a Flight Systems PMD, one of the fairly recent reviews (early 2020?) said that Dorman had purchased Flight Systems and FS is no longer the quality product it used to be. What is your opinion on this?

My son has the lift in my shop tied up... hopefully it will be available in the next day or so and I can get my truck in there and check it out.


Thanks again for your help.


Regards,


Smitty

[DmaxMaverick]

You should have voltage at the LP when the key is turned to START (not necessarily only when the starter has power).

The OPS is independent of the START cycle power. The OPS should power the LP when you have oil pressure (running engine). The OPS is a usual suspect, and the power should be relayed at your soonest convenience, to reduce the load it is carrying.

As Robyn said earlier, the 1995 models are unique in that, the LP can be powered/tested w/o starting the engine or messing with jumpering any wires, simply by moving the shift lever to any position other than P or N, and turning the key to START. This process does not include any input from the OPS.

[utah smitty]

...

As Robyn said earlier, the 1995 models are unique in that, the LP can be powered/tested w/o starting the engine or messing with jumpering any wires, simply by moving the shift lever to any position other than P or N, and turning the key to START. This process does not include any input from the OPS.

My truck doesn't have an automatic transmission, it has the NV4500 5 speed manual tranny. Does it matter what gear it's in when I do this test?


Regards,


Smitty

[DmaxMaverick]

Ah! Totally different, and the previous suggestion doesn't apply, entirely. You still have a clutch pedal lockout. They are almost always bypassed at some point, so you may want to check that. It won't cause a stall, but it can cause a no-crank.

[utah smitty]

Ah! Totally different, and the previous suggestion doesn't apply, entirely. You still have a clutch pedal lockout. They are almost always bypassed at some point, so you may want to check that. It won't cause a stall, but it can cause a no-crank.

Thanks. The engine cranks fine, it just doesn't fire, and there is no fuel getting to fuel filter. I opened the vent cap while it was cranked and no fuel came out...


I'm wondering if the ignition switch might be bad. One thing I noticed is that the dome lights tend to glow dimly after I turn the engine off. Almost like there's electrical feedback going to them... hmmmm..


Smitty

[Robyn]

Check for power to the fuel pump first.

If no power then wring that out and see what the issue is and get power to the pump.

One thing we have not touched on...
The 95 trucks do have a fuel pump relay in the relay/fuse panel under the hood.

Before you get all wild on tearing into stuff.....replace the relay......THIS RELAY is only used during starting and is activated by the starter solenoid circuit.

You may also have a failed OIL PRESSURE SWITCH

The switch on this year has to sets of contacts....one sends current to control the gauge and the other powers the lift pump as soon as the engine has oil pressure.

If the oil pressure switch feed fails the lift pump will not run.

If the lift pump relay (Fuel pump) fails the lift pump will not energize during starting..

Under an ideal situation the transfer pump in the Injector pump will pull fuel from the tank, but if things are not perfect ....as in dirty fuel filter ......????? the transfer pump may not be able to get the job done.

If the OPS circuit has failed AND the relay too then there is nothing to get fuel to the engine.

Check the relay.....they are cheap.

If this gets things going.....

Replace lift pump with a good DELCO pump
Replace the oil pressure switch DELCO

The cheap parts store Chinese switches are junk......Or install the relay kit

Give this plan a whirl.....

[utah smitty]

Thanks for the suggestions and information.


I pulled the Fuel Pump Relay out of its socket and put it back in, and the engine fired up! I'm not sure what the cause is, but another scenario might have caused this problem...


I had taken the truck to my out of state property and back, 250 miles round trip. The fuel gage showed a quarter tank left, and I have had it even lower in the past before refueling... HOWEVER, I recently read of problems with the gages on this series of trucks, the fuel gage being a major offender.


I'm wondering if it was out of fuel?????



I had put 1 1/2 gals of fuel in it before trying to start it the second time, but, if the lines were empty, it may not have had time to get fuel to the IP.



I've tried to start it a couple more times since then, so it possibly may have finally got fuel to it this last time--it snorted and bucked for a few moments before finally starting and running.


So... maybe this was the root cause...


That being said, I still plan to replace the lift pump, the fuel pump relay, the oil pressure sensor, and install a lift pump harness and relay.


I also want to get another PMD... for a spare. It has an OEM Stanadyne in it right now.


My question--the PMD is right behind the front bumper... that's VERY inconvenient for me to get to due to bad knees and back... if I had to replace it on the road, etc. it would be a problem.


Is there another place I can put the PMD where it will still avoid getting overheated and allow easier access?? I've seen a video where one person put it on the driver's side firewall, between the fender and the brake booster. Let me know what you think.


Smitty

[DmaxMaverick]

No PMD mounted in the engine compartment! Ever. It's better off left on the IP. You can mount it between the battery and front clip. It isn't as good as under the bumper, but better than just about anywhere else. Align the heat sink with the headlamp slot so it gets a stream of fresh air.

[Robyn]

Good to hear of some progress.

What color is the PMD....BLACK OR GRAY

Gray is the "New updated" version

I still like the Flight systems units better.

If you have a gray PMD ......These have a different plug on them than the standard black ones.

Another thing.

Be sure that the plate (Heat sink) the PMD is mounted to is very flat and BE SURE TO USE HEAT SINK COMPOUND BETWEEN THE PMD AND THE PLATE (Same white paste as used to mount a computer processor)

HEAT KILLS THESE THINGS....

Good luck

[a5150nut]

On my 94 there was an opening in the bulkhead left of the radiator in front of the left battery. That's where I relocated my PMD to. Made my own extension cable by soldering and using heat shrink tubing.

[Robyn]

Cool air.....I have seen a few folks mount the PMD on a liquid cooled heat sink with it's own little cooler pump....

A bit of overkill.....but keeping the heat down is important.....

[utah smitty]

Thanks for the many replies. I ordered a bunch of things for the truck and they started coming in this week.



I installed the Leroy Diesel lift pump harness with the push button switch to manually run the pump. The pump is now very noticeable... my old pump may not have been working.


I swapped out the old flat panel air filter for a round one from a '97 K3500. In measuring the surface area between the two filters, the round one has almost twice as much as the flat panel. I've attached a photo of it.



I'm also relocating the PMD to the passenger side between the battery and the headlight... but down lower, closer to the turn signal.



If I remove the lower snorkel, will that cause a problem for the air cleaner?



I had read that it's a good idea to remove the "snorkel" for the air filter as it restricts air flow.



I've also got a 4" Diamond Eye exhaust system, and will be installing an EGT gage, along with a boost gage. I'll be putting in a manual adjustable waste gate. What size belt do I need to bypass the vacuum pump?


Anyway, thanks again for all the input.


Regards,


Smitty

[utah smitty]

Good to hear of some progress.

What color is the PMD....BLACK OR GRAY

Gray is the "New updated" version

I still like the Flight systems units better.

If you have a gray PMD ......These have a different plug on them than the standard black ones.

Another thing.

Be sure that the plate (Heat sink) the PMD is mounted to is very flat and BE SURE TO USE HEAT SINK COMPOUND BETWEEN THE PMD AND THE PLATE (Same white paste as used to mount a computer processor)

HEAT KILLS THESE THINGS....

Good luck

The Flight Systems PMD comes with a pink colored "gasket" that's supposed to go between the PMD and the heat sink. Should I use the heat sink paste also?


Thanks,


Smitty

[DmaxMaverick]

The Flight Systems PMD comes with a pink colored "gasket" that's supposed to go between the PMD and the heat sink. Should I use the heat sink paste also?


Thanks,


Smitty

One or the other, NOT both. If both surfaces are perfectly flat and smooth, the gasket is fine. If the surfaces are rough or you are uncertain, the CPU paste does a better job of ensuring positive heat transfer.