93 idi loses power

[Thesilverfox]

Hello everyone! I’m new here and could use a little help.


My 15-year-old son bought his first truck about two years ago. It’s a 1993 F-250 4x4, 5-speed with the Banks Power Pack. Over the last couple of years I’ve learned a little about these trucks, but I grew up around 12-valve Cummins engines, so these IDIs are definitely a different animal!


Here’s the issue. About a year ago we had the injection pump rebuilt, and while it was apart the shop turned the pump up a little. After I reinstalled it, the truck ran great. It smoked a little more than I liked, but it had noticeably more power and would cruise at 70 mph without much effort.


Since then we’ve hauled a few loads of hay with it, and now it’s a completely different truck. It struggles to do 60 mph. Sitting still, it revs clean and sounds normal. But once you’re driving it feels like the injection pump isn’t getting full rack travel. I have to keep the accelerator on the floor just to maintain 60 mph.


Could the timing have slipped? Is there something else I should be checking first? It does make boost, but it’s mostly on the low end. Once the RPMs come up, boost falls off and it feels like the engine just runs out of power.


I’m not sure where to start, so I’d really appreciate any advice from those of you who know these IDIs better than I do. Thanks in advance!

 

[XOLATEM]

I have not been on here for a while but something made me have to chime in here and get something started.

I feel confident that you will get plenty of help from this group. They have always been real helpful to me.

Just making a stab at it but if it were me I would tee in a pressure guage, duct tape it to the windshield (outside) and watch what it does on crankup and running down the road.

That would tell you if you are having trouble getting fuel to the injector pump.

Is there a port on your fuel filter housing that you would be able to tap into ?

Just spitballing....

Take care,

X

 

[Olds64]

You might try to start by doing the ol' ATF trick. Fill the fuel filter with ATF, run the truck for about a minute and then shut it off. This will fill the IP and the injectors with ATF. Then let it sit overnight. The detergents in the ATF will clean the innards of the IP and injectors.

Timing your truck requires a luminosity probe or piezoelectric spark adapter.

 

[ihc1470]

I would tend to agree with SilverFox. I would also suggest a possible plugged fuel filter. All it takes is one or two bad tanks of fuel. Does the fuel filter light system even work anymore? Doubt the timing has slipped, if the fuel pump was loose enough to turn I think you would have much bigger issues going on at this point.

 

[scsmith42]

I would replace the fuel filter first. They are cheap and it's the most likely culprit.

To answer your question, yes the pump timing could have slipped if it wasn't properly tightened. But replace the filter first.

 

[DirtyWood]

When you reinstalled the injection pump did you time it or did you use the old timing marks?

 

[Thesilverfox]

OK guys so we played with it this afternoon I advanced the timing but maybe barely a 16th of an inch more like a 32nd from my Mark that I made when I took the other injector pump off had a longer start. We took it for a test drive still wasn’t good. Brought it back to the house actually found that the throttle linkage was hanging up and would not let him get WOT I fixed that still prolonged start took a test run. Truck did much better but we only hit about nine psi so we brought it back to the house and let it cool off. Rolled the injector pump back to the original timing mark fixed the throttle linkage for what we think will work for right now. this test run We did a hair over 10 psi click it had a quick startup and a lot more responsive while driving like I said, got a hair over 10 psi. I think I’m gonna try retarding the timing and see what she does.

You know, sometimes it’s embarrassing doing these things because you can’t figure out problems until you start asking questions like you can’t figure it out and then when you really start working on it you say it’s just something simple however I think the truck should be making more power than what it is right now and it is definitely more responsive. We’re able to give it more throttle, but I feel like they had. The timing advanced too far so we’ll see as far as the fuel filters the fuel filters actually new. This truck hasn’t had 1000 miles put on it since the injector pump was replaced on it. He only drives around the farm so I guess y’all standby. We’ll see what I get out of it when I retard the timing a little how many psi should this truck be running with the banks power pack on it? I’m curious I’m not sure trucks I used to drive from this time era would do 30 to 40 psi I don’t think this truck will do that so is 12 the magic number 13 or is it just 10?

 

[DirtyWood]

What do you mean by "Banks Power Pack"? The only thing that comes up is an air filter housing for non-turbo engines but you have a turbo.
Also, is there an EGT gauge installed on the vehicle? If not I would do it sooner than later and then you can safely increase the fuel delivery on the injection pump.

Timing on an engine with a turbo is often 7 to 8 degrees BTDC. I have tried more advanced timing but it always seemed to result in less power. Engine should start immediately on a cold start if glow plugs are working properly, no smoke at idle, and no smoke on acceleration unless flooring it.

As to boost numbers, remember that the 7.3 IDI has a compression ratio of 21.5:1 and the 5.9 is 17:1 so comparing numbers is moot. Increase fuel and you\ll see more boost. Safe boost pressure seems to be 10-12psi on stock head bolts. I live in the hills and worked a non-turbo 7.3 IDI for many years and I had 0psi boost, so even 10psi ought to pull plenty in flat Texas.

One other thought is the oil cooler might be due for a rebuild if it's original because the o-rings inside are most likely quite brittle by now.