Need advice with fuel delivery issue.

[Suleiman Saadeh]

1994 F250 7.3 IDI

Truck will start sometimes but other times not at all. Drives fine once it cranks. No irregularities. I was getting air in the lines so after some digging i found a leak in mechanical fuel pump and replaced it along with the rubber grommet around the metal pipe going up from the pump to the fuel filter. I have a clear vinyl line replacing the return line running from my front most driver side injector to the top fuel injection pump to see if air was still coming through after the new fuel pump was installed. It cranked up after I installed the pump and I watched line till no more air came through except the extremely tiny bubbles that I assume are normal. (Correct me if I'm wrong). It started fine after the lines filled up with diesel. Drove it around, came back home. Turned it off. Came back 30 minutes later and it wouldn't start. There was a big bubble in the return line that floated up from the injector and while it was being turned over the fuel in the return line wasn't moving like there was no pressure from the injection pump but there was pressure an hour before and that is what keeps happening. But the Schrader valve would pump fuel.

I'm not sure if the injection pump is going bad or just needs maintenance. I cant say for certain without purposely trying it out but it seems like when the engine is cooled and not been ran itll crank up but once its warmed up and the engine is hot the fuel injection pump does not push fuel.

I'd greatly appreciate some advice or feedback. I've looked for a thread as close to mine as possible before posting but havent found one that quite fits mine.

 

[Thewespaul]

Unfortunately sounds like you need a new pump, when the ip gets heat soaked the tolerances open up and the pump cannot support the pressures needed to fire the injectors. When the truck doesn’t start, you should be able to pour cold water onto the back of the pump and it should fire up.

 

[210Tumbleweed]

How many miles on the truck?

 

[210Tumbleweed]

I don't have the dreaded "heat soak" issue yet...and an original IP with a tick over 140k.

 

[Thewespaul]

I just replaced the original pump and injectors on a truck with 207k, the owner used it to pull a 5th wheel around the country so the truck got a lot of highway, and it was meticulously maintained, never ran out of diesel, as well as always had stanadyne additives used in every tank, it just now started having hot start issues, and the injectors sprayed great after removing them. I’m not a believer in the 100k limit to our fuel systems, because with the proper maintenance I’ve seen them go double that.

 

[Suleiman Saadeh]

I believe you were correct. I tried to start it and it was still hot. Wouldn't start. Pulled a bottle out the cooler. Poured it on it and it fired right up. It's got 234k. Runs like a champ. Has no lag and lots of power. That has been the only real major issue its had outside of needing a starter.

I really appreciate the advice man. I've been trying to figure out what's wrong for months. Never made my own post on a forum but I also never put two and two together about the heat till today.

Is there any way to rebuild the pump cheaper than buying a new one? Or is a new one necessary?

 

[Thewespaul]

There’s no new pumps any more, all are rebuilt units for the most part. Unfortunately there’s no cheap way about it, it’s the most expensive part on these engines, it’s worth the money to get a quality rebuild. Just the parts alone I put in to rebuild cost 600-700, so factor in the cost of labor and it gets pricey. Anything much cheaper than that, not all the wear components are being replaced that need to be, and you will be replacing the pump again much sooner than later.

 

[Suleiman Saadeh]

Yeah that's what I figured. I didnt mean new just rebuilt/like new in the sense it's not been used on an engine. I really appreciate your input. You were spot on it seems. I'll be buying me a rebuilt IP before too long. You have solved the mystery that has plagued me the last several months

 

[Suleiman Saadeh]

Isn't there a certain way you have to remove the IP to not mess up the timing? I read that somewhere and figured I'd ask to get a straight answer.

 

[Thewespaul]

Remove the pump from the gear cover, and leave the cover in place. This will keep the gear in time with the cam, but you will still need to retime the engine once you replace the pump. Pumps should be replaced with injectors as a pair, as they wear at around the same speed. This makes it a pretty expensive part replacement, so if you’ve got a pyro, I can buy you some time with a few adjustments of the governor assembly, metering valve limitor, and at last resort the fuel screw. With these adjustments you can bring the pump pressures back up to help it start hot, and it will give you more time before needing replacing. I’ve stretched out a worn pump this way for over a year in tough times. If your interested let me know and I’ll tell you what you gotta do.

 

[Suleiman Saadeh]

I definitely will my man. I greatly appreciate it. I'm gonna see how it goes over the next few days and see how easily it starts with cold water when necessary. I generally just leave it running when I'm at work because I go job to job all day. I've got some stuff to pay over the next several weeks but after a month or two I can probably buy a rebuilt one with the injectors in a couple of paychecks or so.

I imagine there are tutorials and videos on timing an engine. Is it rather in depth or is it fairly simple?

 

[Thewespaul]

Very simple, but requires timing equipment that is difficult to acquire these days, there are several vendors who rent this equipment.

I’ll take some pictures for you and make a post with the details tomorrow.

 

[Suleiman Saadeh]

Thank you man. I really did not expect so much help like that. Can I not use one of the time tools they have at Autozone or do I need something different.

 

[Thewespaul]

Happy to help, that’s what I’m here for. The timing equipment is specific to these engines, you can’t time them like a sbc because there’s no spark.

Okay, first adjustment is marked in blue, this is known as the torque screw, if your pump is original to the truck yours should have this. Break the locking nut loose and back the screw out 5 turns.

You must be registered for see images attach

Next adjustment is marked in red, this is your minimaxx adjusterment, once again break the locking nut loose but this time go all the way in with the screw until the lock but runs out of threads. This may raise your idle, which you can adjust with a flat head on the throttle bracket.

You must be registered for see images attach

Test and see if those adjustments fix your hot start issues, if they don’t then take this triangle plate off and turn the engine over until you see an Allen appear. You will turn this clockwise, go a quarter turn at a time then re-assemble and test the hot start. These last adjustment will increase the maximum fueling of the truck, and can make it quite Smokey if you don’t have a turbo. I’d recommend getting a pyro before adjusting this last one, but an $120 gauge is still much cheaper than pump and injectors, and it’s something every idi should have anyways.

Hope this helps, like I said I’ve stretched out a few pumps this way, and there’s a good chance you can fix your hot start with these adjustments assuming the pump is not too far gone. Keep us posted!

 

[Suleiman Saadeh]

Thanks that is very good to know. You definitely know your stuff. What is a pyro though? You mentioned a gauge also.