Hi All, I'm having a bit of trouble with my 1995 D1 starting and am in need of some guidance in diagnosing the problem. 1995 D1, 3.9, automatic trans, recently changed the oil, installed a temp gauge, put rad flush in.

​​​Symptoms began two weeks ago, after driving into Kansas City, the truck wouldn't start - a warm start condition. After sitting for about two minutes, it fired up, weakly. I drove it out and around the corner, she died on me while driving then restarted immediately and was back to normal. This then happened again about a week ago.
Yesterday, It happened for the third time, but this time it won't start, even after sitting overnight.

IHScouts post to a similar problem, "Warm restart issue is the coolant temp sensor for the ECM. They're cheap, buy another and test. Don't rely on the Check Engine Light or the ECM to light it. If that doesn't bring it around then the fuel temp sensor is next. What's happening is either the coolant sensor is reporting a cold engine when it's not and flooding it or the fuel temp sensor isn't allowing air bubbles from hot fuel to purge (injectors wide open) which vapor locks the fuel line."
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I have the coolant temp sensor on the way, as this seems to be the number one culprit, but i've noticed a buzzing noise coming from the F.I plenum when the key switch is turned off. I haven't been able to determine if a bad coolant temp sensor will completely shut down the vehicle. Here'e a link to a video of the buzzing sound. I'm at a loss.



Thank you for an insight,
johnny

 

i have a few things to add to my original post. just few days ago, twice, i heard something running near the fuel filler door after i turned the engine off. the second time, i assumed it was the fuel pump and when i loosened the cap, it stopped running. i checked the oil level since i changed the oil on friday. it is a little overfilled- the level just touches the "F" on FULL. Maybe a 1/2 quart over. i dont think this is the issue. Started just fine to drive into the garage and then, nothing since. it just turns. very rarely, it seems to want to sputter.

to add, I've been troubleshooting a little in the Kansas heat.

Checked for spark and i'm getting fire, at least at #1 cylinder. good strong spark.

Air filter is new.

Tried to check fuel pressure- i do not have a schrader valve on the fuel rail, so i dont know how i can check. I crawled under and had my son turn the key to see if the fuel pump is running. i didn't hear anything, but im not sure it would turn on if there is plenty of pressure already in the lines. Also, i dont know what would cause the humming in the F>I> cover, i dont see anything in the RAVE that would make a noise like a fluttery solenoid or relay- maybe fuel in lines adjusting to pressure? possibly air in the rails?

Right now, i am thinking coolant temp sensor, fuel temp sensor, fuel pump or fuel filter. I want to check codes, but the reader under the passenger seat does not work and i havent had time to do the jumper thing. havent even found the plug yet.

Any ideas? Im struggling here.

 

Not sure about that whine sound. I had a warm start issue and it was the fuel pump, try hitting the tank with a dead blow hammer, rubber mallet, or small sledge while cranking. If it starts up after you hit the tank dead center with a faint whine sound you know the pump is on its way out.

 

DavC,

Did what you recommended. Nada. Whacked the top of the fuel pump port with a rubber mallet. I could not hear anything running under there. I could even hear the dang vibration noise from the video, but no pump. My question is, does the fuel pump run on startup every time or only when the pressure is low enough?

I swear, i have looked up and down and around for the schrader valve, put my hands all on it, and felt down in places that havent been seen in 23 years. no valve. is there another way to check fuel pressure? can i disconnect from somewhere else?

 

ok. im getting closer.

I checked the fuel pump fuse. PO had a 15A fuse (owner's manual specifies 5A). The 15A fuse is blown. in lieu of a modern two pronged fuse (i recently divested myself of a SIII), i jumpered the fuse. Still no luck. Now, i can say i need to pull the pump, for sure. but, my bigger fear is that the wires may have not been able to handle the 15A. I am hoping they are not fried. Pulling and testing pump tonight. it's gonna be a long day tomorrow.... any other suggestions?

 

hmmm. seems to be getting only 6v to the pump. but im not sure if that is a symptom of something else of just a poor ground.

 

pulled the fuel pump today. it runs just fine. PO had replaced it with an AC Delco EP381.

Replaced the blown fuel pump fuse. Weird though, the manual says it requires a 5A fuse, but the lid of the fuse box says 15A, so i put in a 15A fuse. 16 gauge wire for pump power should take 15A.

Moved on to the fuel filter. One side is rusted in so tight my body weight wont move it. It's now soaking in PB Blaster overnight.

Has anyone replaced a section of the fuel line? I know it's under about 30 psi. Is this too much for a section of rubber hose and hose clamps? I'm not sure how else to get it off if the penetrating fluid doesnt work. pretty sure the old reliable "heat treatment is not a wise option on fuel filter and rubber hose.

 

Is anyone out there?

Thoughts/ideas?

Anyone?

Is there a way to test the fuel delivery past the fuel filter when a scrader valve is not present? Will a faulty coolant temp sensor cause the engine to not run or just hard to start?

 

AB did a video on a '98 fuel filter replacement. Doug talks about releasing the pressure and hacksawing the rubber hoses if need be. Their filter comes with new hoses in their kit.


I have yet to have PB Blaster fail on me. However, ChrisFix likes to use an ATF/Acetone mix that seems to penetrate further than PB, but I have no clue about using acetone near fuel lines so don't quote me.

 

Had a similar issue with my D1 (1997) ended up being the rollover valve under the hood. It shuts off the fuel pump if the truck flips over. The valve itself was OK, but the connectors were burned and not always making good contact. I also saw low voltage at the pump. I cut the wires and tied them together to bypass the valve since I do very little off-roading and the problem went away for about 3 years now.