Looking for ideas and suggestions with lack of power problem that came on

[fellro86]

The subject is an 86 f250 with the 6.9. It used to pull really well, I have tipped the scales at 24,500 a few times hauling scrap with my 40' flatbed. It was being used for just that when it would barely keep going on a pretty much flat stretch of road. The fuel filters got changed, no help. (I run two, one is a water separator from a 6.2 GM, the other is the original factory unit) It has good fuel flow, so the friend that was using it changed the injection pump with one from a 7.3 parts truck. It still barely ran. I fiddled with it and turned the timing up as far as it would go, and it was improving, but still will barely make a good sized hill at 45 with a minimal load, totally out of character for this truck.

I though perhaps since they had taken the gear cover off with the pump that maybe it was a tooth off, (he had already set it, but even the best of us make mistakes) but after taking it all back apart, it is dead on by the marks. I have no history on the 7.3 pump, but thought about taking the pump I had on the motor in to be checked. Any other possibilities for what it could be?

 

[franklin2]

Isn't there a pressure reading you can take for the fuel supply going to the IP? It does have to have a certain fuel pressure supply or it doesn't work correctly I think I read somewhere. Someone probably knows what it is.

 

[MIDNIGHT RIDER]

The subject is an 86 f250 with the 6.9. It used to pull really well, I have tipped the scales at 24,500 a few times hauling scrap with my 40' flatbed. It was being used for just that when it would barely keep going on a pretty much flat stretch of road. The fuel filters got changed, no help. (I run two, one is a water separator from a 6.2 GM, the other is the original factory unit) It has good fuel flow, so the friend that was using it changed the injection pump with one from a 7.3 parts truck. It still barely ran. I fiddled with it and turned the timing up as far as it would go, and it was improving, but still will barely make a good sized hill at 45 with a minimal load, totally out of character for this truck.

I though perhaps since they had taken the gear cover off with the pump that maybe it was a tooth off, (he had already set it, but even the best of us make mistakes) but after taking it all back apart, it is dead on by the marks. I have no history on the 7.3 pump, but thought about taking the pump I had on the motor in to be checked. Any other possibilities for what it could be?

Long time, no hear from.


Do you have a fuel-pressure gauge plumbed in just ahead of the injector-pump ??


How much combustion blow-by are you seeing ??


Are you certain someone hasn't jammed an old coat or such into the exhaust ??


Way back in High School days, some wise-guys took a tobacco-stick and jammed an old rug way up in some guys exhaust.

The poor guy even went so far as pulling the engine, trying to track down the problem.

 

[david85]

Does switching tanks affect anything?

 

[fellro86]

I haven't put a fuel gauge on it to check pressure. It went from had to drag it home to at least drives, but could be possible. It didn't change anything to switch tanks either. The electric pump died, been hearing the Holleys can fail a seal and wipe out the motor, so I have a Carter to try. Been back to running on the mechanical.


As far as exhaust restriction, no issue there, and they would have to jam it in quite a ways... lol. Doesn't seem to have blowby issues, that I can tell any way. Fires up pretty nice when it holds it's prime... This motor was rebuilt shortly before I got the truck, has maybe 50,000 on it since then.

Been pretty busy, so I had to cut back on a lot of things I was doing. This truck has been waiting for me to get back to it for since last fall... Had a pretty heavy classload, plus my wife went through recovering from cancer, so I had to work more to keep everything going. So my time on all the forums got cut way down, just couldn't spend the time on them any more... I get the summer off from classes while I transition from community college to one of the universities, yet to be determined...

 

[david_lee]

does it run smoothly or its it running like crap? you dont have enough description in your posts. useful information to include would be the amount of smoke at idle and acceleration, the way it sounds when it is running, comparission of loaded and unloaded, and a description of any guage readouts you might have when loaded and unloaded or before it started acting up and now. from what i read in all but your last post, the first thing i would do (because it is cheapest) is check that the accelerator pedal is opening the throttle all the way. i could be way off with this suggestion, but i read not long ago where someone else was having a problem with poor power, but the truck ran fine. once he discovered the pedal problem(it was opening the throttle just over half way i think) and fixed it, he said it was like a new truck. worth a shot at least.

 

[fellro86]

It smokes black way easy, but runs smooth and clean at idle. It acts a lot like it is retarded for timing, and responded to cranking the pump advanced, but ran out of adjustment. That is why I thought it was possibly a tooth off. As I was adjusting it, the rev response improved as well, which initially it was running like crap and wouldn't hardly get out of it's own way (I might have been able to out run it, and I can't run very effectively any more!) After cranking the timing, it got to where it was semi-normal, but not back to how it used to be. I haven't run much of a load behind it since all this went down, maybe at most 2000 pounds. It struggled to get up a local hill with a moderate grade at 45 which in the past it would have never even slowed down.

 

[Brianedwardss]

Try taking a jumper wire to the cold advance and see if it wakes up. When I got my current truck, it would barely pull a hill empty truck at 40-45 mph. Putting a wire on the cold advance woke it up and it would actually idle.

Obviously all that did was tell me it needed advanced. Sounds like you are already advanced all the way, but doing this may give you (us) a better idea

 

[icanfixall]

This sounds like the motor isn't getting enough clean air. Check the air filter for any restrictions. Maybe something got sucked up into the filter path or it really dirty. Look for the throttle not opening the injection pump all the way also. Usually lots of black smoke is a pump turned up too far or an air restriction. Removing the original pump with the grear cover has me concerned too but you posted thats timed on the gear ok.....

 

[Agnem]

Considering the history at this point, you have no option but to have the timing set by a competent IDI specialist. The only way to solve your problem will be by eliminating what is NOT the issue using proper troubleshooting proceedures.

 

[sootman73]

it doesn't sound like a timing issue as that is usully a slow change. not the quick power change like you described. timing doesn't just drop off all of a sudden. i still want to know what the fuel pressure to the IP is....

something climb into the intake while it was sitting? wouldn't be the first time i've seen that happen....

with the extra fuel i'm worried about cracked pistons if you dont have a pyro to know what the actual exhaust temps are. My chevy cracked a couple pistons from multiple 1400degree runs(didn't have a pyro for a while and the timing was pretty messed up...) i had a little shock that weekend.

 

[fellro86]

I'll have to get it all back together and see what kind of pressure it is running. Part of why it is back to being better is that the electric pump failed, and as a quick attempt at fixing went back to the mechanical... however, it is pulling through the water separator/prefilter, but I didn't figure that should cause it to not flow right...

 

[sootman73]

wonder if its the fact that the electric pump can push through the 6.2 filter better than what the mechanical pump can pull through it....

 

[gatorman21218]

does it run smoothly or its it running like crap? you dont have enough description in your posts. useful information to include would be the amount of smoke at idle and acceleration, the way it sounds when it is running, comparission of loaded and unloaded, and a description of any guage readouts you might have when loaded and unloaded or before it started acting up and now. from what i read in all but your last post, the first thing i would do (because it is cheapest) is check that the accelerator pedal is opening the throttle all the way. i could be way off with this suggestion, but i read not long ago where someone else was having a problem with poor power, but the truck ran fine. once he discovered the pedal problem(it was opening the throttle just over half way i think) and fixed it, he said it was like a new truck. worth a shot at least.

Was it me? Yeah I just assumed it was normal N/A IDI behavior to only go 70mph and dog going up over a speed bump. I fixed my throttle cable with a little split washer and GREEAAAT DAY did it make a difference. Maybe yours slipped past the first stop and is now pulling on the end of the cable, effictively alllowing you to only give her half throttle.

 

[fellro86]

Got a fuel gauge plumbed in after the final filter, got it back together enough to fire it up for a little bit, and it reads about 5 psi, a bit of flutter, but right around 5 psi.