Engine revs-up when cold

[jimboagogo]

I'm working on a 95 K2500 with a 6.5L in it.It rev's up on it's own cold,also stumbles and smokes black.Only cold.So far I figured it sounds like the optic sens is on the way out(no DTC's).I installed a reman pump(DS5521),same problem.Tried a new computor(Delco).Same problem.I put the old pump and computer back on same problem.It's a little hard to start but it does start.I did notice I didn't think the glow plugs stayed on as long as they should(checked them,had 1 out,replaced it).I noticed with a stone cold engine the scan tool reads 145*(it's around 45*f here).Unplugged the temp sensor the scan tool reads -7*f.It starts better and doesn't rev-up or stumble with the temp sens. unplugged.The engine sounds better with it unplugged(more advance when cold).I plugged in a new temp. sens(Delco)it also reads out of range.I don't know if anyone has seen this already and could save me some time on the repair.The sens has 5v ref to it and has .4 ohm resistance to the ecm on the signal return.Oh yea has lots of fuel supply and no air.

[JohnC]

The sens has 5v ref to it and has .4 ohm resistance to the ecm on the signal return.

that doesn't make sense...

Search the forum for temperature sensor. There is a chart of temps vs. resistance somewhere.

[jimboagogo]

Sorry John I meant to ground.Ok I don't think I'm too worried about the coolant temp sens.anymore.I tried a used Stanadyne PMD I had kept off a pump core that was condemmed for a bad optic sens.I put the used PMD on and it didn't skip a beat when cold.It has a fairly recent Dipaco PMD on it.I also tried a brand new d-tech on it.The d-tech acted up,the reman pump I installed was also d-tech.So my question now is has anyone else had these kind of issues with Dipaco/D-tech parts.I am not 100% sure it's the problem I'll know forsure on Monday morning.Boy o boy I have alot of time and labour involved here.Not to mention some parts I can't return.I have sold alot of D-tech pumps also pmd's in the last couple of years and haven't had any problems thus far.A few years ago I sold some Flyte pumps and pmd's and had lot's of issues.So I guess this is just par for the course.I think I'll stick the the genuine Stanadyne parts and pay the price. Jim

[jimboagogo]

Ok so I decided to hook up the original d-tech pmd before I fired it this morning,because I had put a good dose of FPPF in it on Saturday morning.It fired and ran flawless.So I'm thinking it was getting air from compression entering via sticking injectors when cold.So it makes some sense that it ran better with the temp sens. unplugged(putting fuel to it a little further down).So the customer is going to try it and let me know how it works.I have had 6.5's with sticky injectors before but never this particular problem.I guess the learning never ends,I'll post if it works or not. Jim