No Start when warm

Hey guys I bought a 1995 GMC 3500 with the 6.5L and am having some issues with it.

When the truck has been sitting for a few hours plugged in or not (cause it’s that cold already in AK) it does a hard start and then runs fine at idle and with easy driving. When it’s be fired up no matter how long it’s been run and you shut it off it won’t restart for about an hour it just turns over.

Also when at a dead stop if I get on it hard it takes off fine and then once it gets out of first it acts like it is starving for fuel.

I replaced the lift pump when I first got it cause they guy said it was bad (test confirmed that) but other then that I have no idea what is going on this is my first diesel and every shop I call doesn’t know much about the 6.5

HELP please

Could be several things..

Starter not spinning the engine fast enough ....

Injector pump is going south and cant build enough pressure to pop the injectors after the pump gets warmed up.

Somebody installed a set of high pop injectors on an engine with a worn pump

Low compression

If the engine spins pretty good speed on the starter...try adding a gallon of ATF to the fuel tank

Mix with diesel and then add to tank....This will THICKEN THE FUEL and if the rig starts better you have a bad INJECTOR PUMP

Any codes showing CHECK ENGINE LAMP ????

When was the fuel filter changed.

Be sure the lift pump is working.

LH FRAME RAIL INSIDE UNDER THE DRIVERS SEAT AREA.

To activate the lift pump on a 95

Park brake on

Tranny in D turn key to start.

Engine will not crank...but lift pump should run.

NICE PURRRRRRING SOUND ...AND YOU SHOULD GET FUEL FROM THE AIR BLEED ON THE FILTER IF OPEN.

Also WITH ENGINE RUNNING OPEN THE WATER DRAIN (Fuel FILTER) NEAR THE TOP OF THE WATER CROSSOVER AND YOU SHOULD GET CLEAR FUEL and engine should stay running...

If engine dies then the lift pump is not working.

Oil pressure switch near the glow plug relay at LH rear of intake manifold above the bell housing flange controls fuel lift pump.

Switch can die and the lift pump will not run.

If the lift pump is not running when the engine is running this can cause LOW POWER.

Run the engine and crawl under and see if the pump is vibrating.

Check for fuel flow at the drain even if the pump is running.

Filters are always suspect.

Add fresh filter (Clean out housing well)

Run lift pump with the tranny in D ENGINE OFF KEY IN START TO BLEED OUT THE FILTER

Get a helper....

Check the filter and lift pump.

I crudded up filter can and will cause terribly poor power..


If your filter is good and the lift pump is delivering fuel at the drain and the engine runs....and then things are still not good...proceed farther.


Let us know what you find

Robyn

Engine spins fast like it should

Only check engine light that come on is when it’s going up a hil and throttle is over a 1/4 or going down the highway around 60 65 it pops on and off but it’s never stayed on

I’ll run the rest of the test on it probably tomorrow for the lift pump and other thing and let y’all know
Thank you

If you are getting a check engine light there should be a code stored.

Pull the codes and see whats stored.

Well now it’s not starting at all!

Went to work and was backing into a spot and it just died right there and came out to it this morning and no start at all it turns over great and I did the lift pump test and hear it running but no starting

Does it smoke when you crank it over? If not then there's no fuel; either the fuel's not getting to the injection pump or it's not injecting.

Have you checked for DTC codes? Have someone crank it over while you look for fuel at the drain line.

No smoke when trying to start, trying to find a scanner to scan it, had someone turn it over while looking at the drain tube to see if it’s getting fuel and it pours out of it so it’s getting enough fuel just not even studdering when trying to fire up

It's a 1995. A paper clip is your scanner.

https://www.thedieselpage.com/members/trblcode.htm

First suspect at this point is the PMD

A failing PMD can cause several symptoms.

Hard starting when hot...
Check engine light on and off (Usually a response time short or long code)

And finally a stall and a no start.

Has the PMD been relocated off the IP ????

Flight systems makes a good one.

Be sure you install the proper resistor (If the PMD is off the IP you can see what resistor is in the plug socket on the PMD ) If the PMD IS ON THE PUMP...USE A #5 RESISTOR

Always mount the PMD ON A COOLER...PREFERABLY OUT OF THE ENGINE BAY

It didn’t start happening until winter hit and the diesel fuel got thinner at the pumps for winter time (in stationed in AK)

Also the PMD is relocated off the pump

I would suggest trying a KNOWN GOOD PMD (NEW ONE)

How old/miles on the PMD in the truck

PMD'S are a consumable on these trucks.

Lifespan can be a long time...or as little as 10 15 K miles.

Where is the PMD located.

NOW ......

Remove the fuel inlet hose from the IP and stuff it in a container and energize the LIFT PUMP.

Having fuel at the drain line is good, but does NOT mean fuel is getting to the IP itself....THE FUEL TO THE DRAIN DOES NOT FLOW THROUGH THE FILTER

When was the filter last changed ???

Ever use BIO DIESEL ????

That stuff can clog a filter real quick