my 93 cummins in my chevy is idleing itself up and down after a couple of hours of driving hasnt got real hot 195, not ticking from the fuel pump, the transfer pump is brand new. IT is a 160 horse 400 foot 93 innercooled any ideas

 

Just puttin ya back on top!

Thats a new one by me, someone will chime in with an idea, hang in there.
Can you maybe get a video of it doing it then post it up? Might be a big help in diagnosis.

I am going to be doing a conversion on my '91 OLD body GMC crewcab, maybe you can give me some pointers? Shoot me a PM if you would please?
I do have a big question about clearing the hydroboost with the intake.

 

Mine did the same thing when we bought it. After driving it with fuel additive, its OK now.

 

I will try a little additive I Have a gallon of power service I keep handy And I will spin on a new fuel filter and try it again.

 

put some fuel additive in the tank and drove it around for about an hour this morning it seemed to idle fine it really puzzles me that it would do that. I held my hand on the pumo linkage yesterday while it was doing that and i could not feel any movement I worry this could be a prelude to a pump failure anybody rebuild ve pumps?

 

does the truck start fine after everything gets good and hot?

 

yeah it fires right up and runs for 20 or 30 seconds then it will idle up for a few 20 or 30 secs then idle back down for a few minutes till it idles back up again

 

Is the A/C on by any chance?

 

no the truck dosent have ac ,sure wish I would hurry up on that one, And I have the grid heaters on a lock out switch it is 85 here in arizona right now so i dont use them nothing else on the front of the motor

 

my truck was just doing the same thing to me. I went to the local pump shop and talked to them and they said from the new fuel the governer weights might be sticking. I took the top part of the pump where the fuel pin rides in and they rebushed it and have me a new o ring for free. they also said that might have been why it was idling up and down cause it was just weeping fuel around the throttle shaft. when I ask what I should do about the governer weights sticking he said next fill up throw a quart of fresh oil with it and that will lube them up.

 

Ive been driving it hard last couple of days but I have put some extra diesel treatment in the tank and no problems I will look into the governer weights thanks for response on that, what do they do on the new pumps to solve the problem there.

 

idle still going up and down on its own got the pump lubed with power service any body had to rebuild a pump over this. I wonder if it is not the fuel shut off solenoid any thoughts

 

Got any fuel leaks at all? Air in the fuel will make them run funny.

 

Finally took the top of the pump and the inside was amazingly clean probably after all the fuel cleaner Ive run through there. I went down the fuel lines checked all the fittings checked out the lift pump and made my way to the tank pulled the tank down took out the nozzles and felt kinda silly for not having checked there first, the lift tubes were for the gas chevy motor when I bought the truck originally it was a diesel but the fuel tank must have come off a gasser the vapor trap on top only has a couple of tiny little holes that catch the vapor return collect it then let it drip into the tank these little holes had filled up with gunk and looked like they had rusted a little bit for condensation so the diesel returning from the motor could just barely drip into the tank drilled out the vapor trap cleaned it up put it back together now it runs like a top,I am just glad it was a simple fix this time but I will have to wait to see what the consequences of this will be