Rebuilt 89 7.3 will not idle or go over 2100 rpm

[BryantMarwitz]

Let's me catch y'all up to speed on this project truck that has been years in the making. Roughly 3 years ago I pulled the engine because she was basically running on oil. over the course of the next 2 years I got the block and heads rebuilt. I had the machinist put 910 comp springs in the heads and I put the R&D camshaft in it (this engine is currently NA) cylinders are over-bored .30. About a year and a half ago we finally got the engine in and we bolted everything up, but the engine would not start. (I made a post about this back then) college started and I was out of time so I had to let the truck sit. fast forward to two days ago I finally got a week where I can work on this thing. To make an already long story shorter the old lift pump was no good, and the FSS was no good on a basically brand new IP pump from R&D. I switched it out with the OG pumps FSS. Finally the truck fired, it was a good moment I've never rebuilt an engine before and I wasn't sure if this thing was ever going to work.

Now to the problem. The truck runs fine and sounds beautiful, No smoke out of the tail pipe, just glorious sound. The truck will not idle though, if I hold the pedal down to keep the rpms around 650 rpm it will run but if I let off the pedal the truck dies. Not only that, but I cannot get the truck to go over 2100 RPM and the throttle response is really bad.

The truck has basically all new parts with few to no miles one them. Injectors are stage one R&D injectors, R&D 90cc IP pump, new fuel filter and a new lift pump. I'm not really sure what to do next I am figuring that something may be gummed up in the IP pump from sitting so long but I'm not sure. Any feedback would be welcome.


Thanks!!!

 

[quickster]

If you have to hold the throttle down to hold 650, it sounds like your throttle cable. You shouldn't have to hold anything down to stay at 650. What's your truck? There are a few different lengths throttle cables. Did you try to operate the pump with your hand? Try the simple stuff first. I installed a pump that was sitting on a shelf for years and I had no idle or running issues. Did you replace the cable? Maybe linkage on the pump?

 

[BryantMarwitz]

I wish it was that, the truck will not start unless the you move the throttle on the pump forward. So, if you unhook the throttle cable the engine will not start. Unless someone else is outside and moves the throttle linkage on the IP pump.

The truck is a 1989 F-250 7.3 IDI, with a ZF5 manual transmission.

 

[quickster]

That doesn't sound right. Was the linkage on the pump removed, or adjusted after you put the pump on? And the fuel shutoff was bad too? Something doesn't sound right. And just curious, you didn't remove the pump tower, did you? The housing over the gear the pump mounts to.

 

[IDIBRONCO]

If you have to hold the throttle part way down to get the engine to run at 650RPM, it's not idling high enough. Try adjusting your idle speed screw to make it idle higher. As for the sluggish throttle response and the low maximum RPM, try doing the ATF trick where you fill the fuel filter with ATF, run the engine for 30 seconds or so (you can hear the difference in sound when it's running on the ATF), and then let it sit overnight.

 

[BryantMarwitz]

Considering the engine has been rebuilt the whole assembly has been off. I have it all lined up though on the timing marks. Also the IP pump sat for a year and a half with diesel in it which is why I am thinking it may have some gummed up internals.

I already have ATF in it and that made a difference. I've gained about 1500 rpm since I first got it started early today (when I first started I could only get about 1000 rpm out of it) the throttle response is better now as well. We will see how much of difference the ATF makes by morning.

 

[Big Bart]

Have you checked the IP timing? Timing on these trucks is everything.

 

[Rusgo]

Unless the timing is way off, it should still start and idle fine. I can move the IP back and forth a couple dimes and the average person would never notice the difference in sound and performance

I'm guessing this is the first time the R&D IP has been installed? Timing does fluctuate from pump to pump so just aligning the marks leave error that only a proper timing job can correct. That won't stop a decent idle though

And the throttle linkage can be completely disconnected and it should still start and idle. Just won't kick up into high idle

Sounds like things are settling in a little bit. Curious if it'll keep on improving with the atf

Does sound like it's starving for fuel. It doesn't take much fuel to get the engine to 3000 rpm in park/nuetral

I second disconnecting the throttle linkage and seeing if manual operation gets the RPMs up more. Just to eliminate cable binding as a possibility

Sometimes I unscrew the fuel filter a touch to check how much fuel comes out past the filter gasket during cranking. Let's you know if the lift pump is doing any work.

I've left my electric lift pump turned off and the truck still started and ran for hours on the highway (oops) So just because it's running doesn't mean it's getting good fuel volume or that there is no air in the system

 

[IDIBRONCO]

Timing does fluctuate from pump to pump so just aligning the marks leave error that only a proper timing job can correct.

I may have been wrong, but I read this as the marks on the gears were all lined up correctly. I first thought about timing until I reread the part about no smoke out of the exhaust. Timing that far off would definitely put off colored smoke.

 

[BryantMarwitz]

So here's what has happened since last night. I adjusted the idle screw and now the truck idles just fine. The idle screw was turned all the way out. I probably unscrewed it all the when moving the bracket around or something. Now it does idle fine, although occasionally there are weird fluctuations in RPM. The truck will jump from 650 RPM to 1000 on it's own. The timing advance is unplugged, The only thing hooked up to the IP pump is the wire going to the FSS.

The truck still will not go over 2100 to 2400 RPM. The maximum RPM the engine will run at is a little bit different every time you let the engine come back to idle and give it throttle again. Now that it will idle I have disconnected the throttle linkage and manually gave it throttle but there is no difference between having the throttle hooked up and unhooked.

I've tested the fuel flow through the schrader valve and at idle a decent stream comes through. At full throttle it only barely leaks out, I am not sure how much flow should be coming through there though.

The IP pump probably a couple thousand miles on it and the injectors only have a few hundred. Both are basically brand new though. My worry is that there is something wrong with the camshaft timing since I got the R&D stage 1 camshaft. I'm almost positive I put it in there right, 1 tooth the right of the mark or however it is supposed to go. I'm curious how the truck would run if it was off a tooth? would it sound and run great with no smoke and just not put any power down?

I'm leaning towards it being an issue with the IP pump or fuel delivery to the pump, but I'm not sure what a truck a tooth off would run like.


Again Thanks for any feedback!!!

 

[TNBrett]

Have you spoken with Justin at R&D about it? It’s his pump, injectors, and cam. I think I would want his opinion on it.

 

[IDIBRONCO]

the old lift pump was no good,

So what did you do to remedy this? I don't recall you saying.

Have you spoken with Justin at R&D about it? It’s his pump, injectors, and cam. I think I would want his opinion on it.

X 2 on this one here.

 

[BryantMarwitz]

After messing with the truck most of the day we've come to the conclusion that the IP pump is and was very gummed up. After taking the FSS cover off multiple times and jiggling the metering valve and governor spring we continued to get better throttle response and higher RPM out of the engine. I also filled the fuel filter with half Lucas injector cleaner and half seafoam this significantly improved throttle response and max RPM.

I'm not sure if I should take the pump somewhere to be taken apart and thoroughly cleaned or just keep messing with the springs and running cans of seafoam and Lucas through it. The truck will do about half of what it can do at full throttle. At idle the truck will hit 3200 RPM. However, going down the road acceleration is about half of what I remember.

 

[IDIBRONCO]

Well you're getting closer. Have you let you cleaner sit inside the IP overnight and see what that does? I also like Hot Shot's Diesel Extreme for IP/injector cleaning. One more question. Did you put any fresh fuel in the tank or are you running the old stuff? It may make some difference.

 

[The_Josh_Bear]

+1 to keep de-gumming the IP with diesel cleaners. Fill up the filter, run it for 20-30 seconds and shut her down for the night. Would be sweet if it all works out.

BTW IP stands for Injection Pump.
So IP pump would be Injection Pump pump.
Kinda like "FedEx Express" = Federal Express Express.

A little closer every day, you might be laying down rubber by the weekend!