Help Needed ‘91 F350 7.3L IDI idles well, runs like garbage.

[Tremar]

Good morning, first time posting here so thanks in advance for any info gained, and all the info I’ve already read through!

I just purchased my first diesel truck, 1991 Ford F-350 7.3l IDI E4OD RWD, and it’s running pretty rugged. A couple of days ago it was starting perfectly, idling for days, but once put into gear it really drags. There’s very little throttle response, it takes forever to get up to 45mph(max speed), it’ll buck and shudder if pushed anywhere close to hard (acceleration wise), and when climbing gears, right now, it has a tough time shifting unless the accelerator is released enough for it to catch up. That’s the overall standing of the truck the past few days, but presently what’s happening is, it won’t crank and start unless I have a helping hand in the cab while I manually give it fuel from under the hood. After she starts up, it’ll idle for days, but all of the same symptoms I mentioned before still take place. Being the newb that I am my gut says there’s an issue with fuel delivery. But, before I go swapping parts because I don’t know any better, I wanted to consult some experts, to see where I should start poking and prodding for some answers?

Below I’ll copy and paste bulleted notes about info I got from/about the previous owner also so you get a better idea of what we’re dealing with here... I’ve also got pictures and videos to accompany for what they may be worth! I have access to tools, gauges, etc so I can try and provide whatever readings may be useful.


Previous Owner:


-Replaced IP, and lift pump. (with Holley MightMite[Located in engine comp, not correct I know, his setting is 7psi.]) I’m not certain if he just bypassed or fully deleted the lift pump.

-Removed entire OEM fuel filter and heater assembly. (That space is where the Holley E-Fuel pump is located)(no filter)

-Did something to governor to “open her up”

-He bought it probably around 06/20, date on title, swears it was driven from here in SC to Florida, NC, etc with no issues... take that with salt and if true assume the issues came from him messing with pumps and governor.

-Brakes are sponges at this point, even though I had the seller bleed the lines because he knew there was air in them. Still garbage.

-Ambulance alternator? He said he put this “brand new, ambulance alternator in. It’s rated at 160A.” (He had to replace the voltage regulator before I could drive it)

-New voltage reg.

-After it stalled on me the first test drive they removed a kink from the fuel supply line and removed all the metal supply lines to the injectors to clean them out because they were “gummed up”. When I arrived back at their shop they tried to turn it over without tightening the lines down and fuel shot all over the engine compartment.

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[79jasper]

I replied on the other forum.
It is a fuel delivery issue.
You last sentence about shooting fuel across the engine, that's technically how you bleed the lines.
You need to do a fuel pressure test. Read pressure at idle and under load.

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[Tremar]

Thanks 79jasper! So, I’ve made a little headway in the process of elimination but the deed isn’t done.. So I call on you again! So I tested and relocated the Holley pump, because it works and everything was closed yesterday. The pump is just ahead of the FSV and is providing a constant push of fuel. Today I went over to affix the pump to the rail and test drive, below are bullets describing how it went;

•Started right up
•No bucking when put into reverse
•No bucking when in Drive
•Throttle response is still mediocre(cable needs replaced btw)
•Fuel delivery seems fine(Still need OEM filter and separator, 60micron in line though)
•Driving it seems like it’s struggling to shift a little, like it can’t quite get there. Sometimes letting off accelerator helps, sometimes not.
•Drove it for around 20min straight(15-50mph, tried to push it a little so the additives would make it into the nooks and crannies.)
•After 20min it started to buck when getting towards 3rd gear I believe. RPMs built but no shift and bucking.
•Died after about 25min of driving on the way back home.
•Looked under chassis, losing a little oil. •Restarted no problem, died again in reverse.
•Restarted no issue again, started to become sporadic in idle, but drove it home gently.
•Parked in driveway, and let it idle just to watch gauges.
•Became more sporadic, dropping and spiking +/- 400rpm until it finally let go and died.
•Looked under the chassis again and there was a decent puddle of oil (dark dark oil, I think it’s oil atleast...)
•Crawled under to try and pinpoint the leak, the starter is covered in oil and dripping onto driveway.
•Checked oil level, even with the leak it’s still a decent amount over where it should be according to the dipstick.
•Checked trans fluid also, to make sure that wasn’t part of the hesitation in gear shifts, according to dipstick its overfilled also.

A.)Where would that be leaking from?

B.) Would that cause the issues while driving now that I have a constant fuel supply?

C.) Should I drain both Oil and ATF to a normal level? Or, should I just change oil filter, and ATF?

It seems now like the bucking and stalling has something to do with oil pressure possibly. Though the gauges read fine, obviously somethings not right with regards to oil/pressure. Again I thank you immensely for any and all help!


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[bcvickers]

Thanks 79jasper! So, I’ve made a little headway in the process of elimination but the deed isn’t done.. So I call on you again! So I tested and relocated the Holley pump, because it works and everything was closed yesterday. The pump is just ahead of the FSV and is providing a constant push of fuel. Today I went over to affix the pump to the rail and test drive, below are bullets describing how it went;

•Started right up
•No bucking when put into reverse
•No bucking when in Drive
•Throttle response is still mediocre(cable needs replaced btw)
•Fuel delivery seems fine(Still need OEM filter and separator, 60micron in line though)
•Driving it seems like it’s struggling to shift a little, like it can’t quite get there. Sometimes letting off accelerator helps, sometimes not.
•Drove it for around 20min straight(15-50mph, tried to push it a little so the additives would make it into the nooks and crannies.)
•After 20min it started to buck when getting towards 3rd gear I believe. RPMs built but no shift and bucking.
•Died after about 25min of driving on the way back home.
•Looked under chassis, losing a little oil. •Restarted no problem, died again in reverse.
•Restarted no issue again, started to become sporadic in idle, but drove it home gently.
•Parked in driveway, and let it idle just to watch gauges.
•Became more sporadic, dropping and spiking +/- 400rpm until it finally let go and died.
•Looked under the chassis again and there was a decent puddle of oil (dark dark oil, I think it’s oil atleast...)
•Crawled under to try and pinpoint the leak, the starter is covered in oil and dripping onto driveway.
•Checked oil level, even with the leak it’s still a decent amount over where it should be according to the dipstick.
•Checked trans fluid also, to make sure that wasn’t part of the hesitation in gear shifts, according to dipstick its overfilled also.

A.)Where would that be leaking from?

B.) Would that cause the issues while driving now that I have a constant fuel supply?

C.) Should I drain both Oil and ATF to a normal level? Or, should I just change oil filter, and ATF?

It seems now like the bucking and stalling has something to do with oil pressure possibly. Though the gauges read fine, obviously somethings not right with regards to oil/pressure. Again I thank you immensely for any and all help!


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Did you check the ATF with the engine running?
How far above normal is the oil level and does it look thin or smell like diesel?
I didn't see where you have a fuel filter in the system; have you checked it after it died in the driveway this last time?
The dying and poor running is still a fuel delivery problem. The only way you're going to solve for it is to place a fuel pressure gauge inline and watch it while it is acting up.