6.5 1994 GMC Yukon "S" Hard starting, cuttouts, ect.


I have a DTC 18 and a 35 code come up all the time- It use to be intermittent but now it's all the time-

I'm looking at the Alldata flow chart

I'm getting 8 cam reference pluses missed-

I unplugged the optic sensor
I've got 5 Volts on terminal "A" and 12 volts on "D"

I'm going to backprobe the "D15" to ground and then if it passes,
I've got a faulty PCM or PCM connection ????

I kind of realy doubt that considering the computers the last thing to go and it has been replaced, due to the intermittent codes and an EGR code that has since been fixed (nothing to do with the PCM in the first place, of course)

Everyone says to replace the Injection pump, but is there any way to tell if that's it or is there any other things to check/scan ?

If I spend 1200 $$ plus on an INJ pump and those DC's are still there I'm going to be in deep ****

Thanks again for the help- Tom

You have a scanner tommyinajar?
Look at fuel pump angle Should be ~30*'s not 60-90*'s
Timing numbers?

DTC 36 is pretty much reason enough to replace the pump.

Sorry typo code 18 and 35 (35/36 about the same anyhow)

I don't see any thing about the fuel pump angle on the scanner ??? (Not even sure what that is)

The Meas INJ is 25.5 deg
Inj PW is 1.6 ms
the TDC offset is -0.4 Deg

Does that help at all ?

Thanks

25.5 degs is some serious advance, does it start?
Could be dirty/watery fuel, bad optical or connections.

Are we sure that "Meas INJ" is the value for timing (isn't it usually 3.5 deg for stock? I don't see the engine even running as you stated qm. The TDCo seems to be right for stock timing.

Mine did this almost exact same thing, and I tried everything to try to fix it, EVERYTHING!!! Except one, replace the IP, so I did, and I have no codes what so ever anymore. But now I have to replace a starter that I burned up after replacing the IP. I know you don't want to hear that, but that is what my experience is with the same situation. Hope it helps, hopefully you can get around replacing the IP, but I couldn't.

25.5 degs is some serious advance, does it start?
Could be dirty/watery fuel, bad optical or connections. If you hold the pedal to the floor, it will start- barely.

I also checked the small section of the 6 wires going to the Optical Sensor (PN 1255 3327) and it seems fine, no opens. Could the wires to the PMD possibly be bad or would that cause a different code or a 'no run'.

I think the "meas inj" is what the OTC scanner is measuring the injector timing at. The range is supposed to be 0 to 25 degrees-

The desired injection (Timing ) is supposed to be at 14 (Range 0-25 degrees).

About 5 Months ago I put in a remote PMD and that stopped the codes for the most part for a while- Was the new PMD covering up for a failing inj pump as someone suggested ??

If I clear the codes they come back instantly when running- It used to take a while...


Hey I don't mind replacing the Injection pump (except for the $:)$)- I just don't want to do it, and have the codes still be there and - ok now I'll replace this....

Any thing else to check/do or should I get out my VISA $ ;)- Thanks

I have a buddy that drive's the sme truck as me, '94 CC K3500, F engine.
He got a tank of bad fuel and The truck died and wouldn't restart.
I put the scanner on it and timing was 25*'s like your but with a ton of cranking the truck would start and timing would go to normal numbers. Does yours do that? iirc my buddy had to put a new optical.

First, it sounds like he has a generic scan tool by the data presented. These can be very "off" in how they measure/display timing.

My suggestion would be to start with a fresh pump...

No it stays right at 25.5 - even when it finally starts.

Its an OTC Enhanced with Pathfinder '97. I know any non Tech 1,2 scanner can be off, but that seems to be off alot, even out of the scanners described "normal range".

Sounds like the optical is out ? The pump was built in 97 '5288' (94 truck) - Next question should I go with a new optical, rebuilt pump, or a new one ??
Heath Diesel has the new one for 1100$ minus the PMD, anyplace else or recommendtions ?

If I were the forum vendor endorser I would mention they sell them (Heath, JK) but if you google it you'll find $700-$900 rebuilt ~$1100 new.

Tommy, the Code 35/36 means your FSOL is worn out, stalling means your PMD is probably toast, 8 reference counts missed means your optic sensor is gone too. Your pump is a goner dude.
Where are you, we can probably help you locate a near by fuel shop to get a rebuilt pump from.

No not the pump !!! :)

Any clue why the 18 and 35 went away for almost 5 months, when I replaced the PMD ?

There is a Huckstorf Diesel pretty close (Wi Huck)- Should I go with the rebuild or the new pump ? ( I'd hate to do it again in 6 months )-

The pump was built in 97 '5288'
If your pump has lasted since '97, your overdue to splurge and get an updated model, ie 5459/5521. Huckstorf's site doesn't show any prices or warranty info, have to call and ask them.

If your pump has lasted since '97, your overdue to splurge and get an updated model, ie 5459/5521 "SPLURGE" huh ?

Every time I stop for Diesel its gets splurged upon- How come when I first bought it Diesel was about .35 cents less than unleaded, now last time I filled her up it was almost .35 cents more.... :D

Less refinement = more $$ ???

It's supply and demand Tommy,
You reduce the supply of refined diesel and demand will stay up. Everything in this country moves by diesel, planes, trains and trucks carring anything and everything. When demand stays high after a doubling of fuel prices, the futures go up, the price at the pump goes up, plus you can probably squeeze two gallons of gasoline out instead of a gallon of diesel from the same crude. That would indicate that the refinement of gasoline has become priorty. No wonder the price of diesel has been higher than premium unleaded for a year down here in the refinery belt.

I don't know about the supply and demand stuff - Every body in Europe wants a diesel be cause its cheaper than gas and better gas milage and no way is it cheaper to produce- Do you know how much stuff the have to add and do to the gas before its fit to use...

Don't ask about it being fit to use around here. They want to keep forcing ethenol on us plus we've got the highest state gas tax already.