Acceleration question for you schooled IDI vets.

[larson]

What's it mean timing wise if I'm gradually feeding the the go fast pedal and my truck runs well but if I just dump the pedal it doesn't seem to be so snappy. It feels like it takes a second to get out of its own way.
The timing is set at 8.5 and marked at 9.4 for future adjustment if wanted. Injection Pump has 50k on it and the injectors are original with 194k on them( yes they are due for replacement I know)

 

[FORDF250HDXLT]

timing too advanced.retard .5 to 1 degree and she should be snappier.

 

[JLtoolman]

I don't think it has anything to do with timing, especially since your timing is right on.
IIRC, this is caused by a lean condition at idle, or lower RPM. When you jump on it, it is probably getting more fuel, but it has to catch up.
In a gasoline racing engine, I would turn up the low end fuel to correct this issue.
The injectors are way past their life, and need rebuilding, or replacing. I would rebuild them if they are original. I have had mine rebuilt twice.
Hope this helps.

 

[chris142]

Mine is the same.bit runs better if I don't hammer it off the line.I have my timing @8 or so but I think it ran best @6

 

[83ford]

All about how much fuel is bein dumped in it.mines maxed so if I just lay in to er it's a slug but if I ease into it it's a lot better


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[icanfixall]

I think the best question is who rebuilt the injection pump? Might be a poor rebuild. But for sure... The injectors are well past the rebuild or replacement mileage. As in injector wear out many things happen. The spring pressure drops and mostly the tip just wears out from the fuel erosion issues. So a weal spring coupled with a worn out tip makes for a messy spray pattern and problems with injection. Say you have 6 good new injectors and 2 weak spring injectors. Those weak spring injectors will pop early and inject fuel way too early in the compression stroke. That will cause a knock plus it slows down the piston causing a loss of power being transmitted to the crank. Same thing as a bad spark plug in a gas engine. Now if all the injectors pop at different pressures you can see the poor crank is being ****** all over the place trying to make power to the wheels. Hope this did not get to simple.

 

[IDIoit]

the very first thing i did when i was working out issues was to install a a fuel pressure gauge at the filter head.
i too want my truck at peak performance.

 

[Dieselcrawler]

After playing with timing on the dyno, Mel and I found 9-9.5 got me the most power. Just food for thought. I set every pump I time between those numbers. Never had a complaint

 

[icanfixall]

After playing with timing on the dyno, Mel and I found 9-9.5 got me the most power. Just food for thought. I set every pump I time between those numbers. Never had a complaint

I agree with 9.0 to 9.5. Not because someone said it works but because someone "proved" it works. I ask or seek out verification to anything I post. Personally I have run as high as 11.4 advanced and that was really too much. Still not sure how I got that far advanced after I was very careful to tighten up the pump at 9.5. But there you have it. Things changed on me. I do not recommend running past 10.0 advance either.

 

[larson]

the very first thing i did when i was working out issues was to install a a fuel pressure gauge at the filter head.
i too want my truck at peak performance.

Where at on the filter head?

 

[larson]

I think the best question is who rebuilt the injection pump? Might be a poor rebuild. But for sure... The injectors are well past the rebuild or replacement mileage. As in injector wear out many things happen. The spring pressure drops and mostly the tip just wears out from the fuel erosion issues. So a weal spring coupled with a worn out tip makes for a messy spray pattern and problems with injection. Say you have 6 good new injectors and 2 weak spring injectors. Those weak spring injectors will pop early and inject fuel way too early in the compression stroke. That will cause a knock plus it slows down the piston causing a loss of power being transmitted to the crank. Same thing as a bad spark plug in a gas engine. Now if all the injectors pop at different pressures you can see the poor crank is being ****** all over the place trying to make power to the wheels. Hope this did not get to simple.

Your guess is as good as mine Gary. When I had it replaced I knew absolutely nothing about the IDI 7.3 other than there was no turbo and it wasn't a psd under the hood. My truck runs well and gets me 19 mpg consistently. I drive it 110 miles a day. Call it stubborn or stupid I know the injectors are pretty much all but done I just have a lot on my plate so every time I think I can buy some something else always comes up. And that's pretty much the story of wants and needs gentleman lol.
Correction my truck runs good other than the whole full throttle slow go post up top.

 

[dunk]

The pump retards timing more as you get into it. As RPM increases it advances. So slamming it open at idle will retarded timing before there is any RPM advance. That's all I can think of.

Think of it like manifold vacuum advance along with mechanical advance on a gas engine. Slightly open throttle gets mechanical+vacuum for efficiency, but hammer down vacuum advance cuts out to avoid detonation at higher load.

 

[Black dawg]

What does the rattle sound like when you just floor it suddenly? Depending how the pump is set up, you could have too little or too much timing......regardless of being set by the book or not. With worn pumps or pumps not set up quite right
(also pumps with the fuel adjusted much either way from stock) sometimes they need a little more or less timing spec to work right under all conditions. Too many people get a carried away thinking this number or that number is the correct timing...there are way to many variables (including personal taste) to say set your timing here...it will be perfect.

 

[icanfixall]

What does the rattle sound like when you just floor it suddenly? Depending how the pump is set up, you could have too little or too much timing......regardless of being set by the book or not. With worn pumps or pumps not set up quite right
(also pumps with the fuel adjusted much either way from stock) sometimes they need a little more or less timing spec to work right under all conditions. Too many people get a carried away thinking this number or that number is the correct timing...there are way to many variables (including personal taste) to say set your timing here...it will be perfect.

With my years of experimenting with timing I too feel a certain number really means nothing more than a place to start. Anyone the rents a timing meter from me gets my suggestion to make 3 timing sets when you have my meter. Before you actually move the pump I recommend that you make a center punch mark in the pump to gear housing joint line. Then you can actually see how much the pump was moved. Then time the engine 2 more times making a center punch mark each time to adjust the pump. Now you have 3 different degrees of timing you can adjust to and know for sure what you have. You can even remove the pump from the engine and reinstall it and still know what the timing is. No other pump will be timed this same way. Every pump needs to be timed to your engine. Mel explained the internals have no marks so every pump is timed differently internally. They can get close but not ever like a chevy small block distributor is.

 

[crash-harris]

Another vote for injectors. I noticed a decrease in acceleration when mine started to go.