95 K3500 dies,,

[94GMC2500]

OK this might get long. I bought this 95 dually a couple years ago. Its had stalling and sometimes not starting problems since I have had it. I have put new fuel tank, new sender, new fuel lines, new lift pump, now wired to run whenever key is on, relocated pump driver and cooler up behind bumper, replaced injection pump wire harness, just put new crank sensor in, replaced fuel shut off on pump, new fuel filter.

Today it started and ran about 10 seconds and quit, and would not restart. First thing I did today was unplug the fuel shut off and checked for voltage with key on, had 12.3 volts, grabbed another shut off solenoid and plugged it in and it worked fine. So I plugged that back together. Then I grabbed a spare pump driver and plugged it in up by the pump, still no start.

So then I took the fuel shut off solenoid out and turned key on and ran some fuel out the hole, put shut off back in and it started, ran rough and quit a couple times but it would restart and then ran fine again. So next I put a piece of clear hose on return out of pump and left it run a long time checking for air, not a bubble. when it does run I can wiggle on wire connections, fuses, relays and cant make it quit. also never get any codes.

It will run a week or two just fine and then the stalling starts up again.

I have no idea what else to do with it. I have another engine wire harness I thought about putting on, or maybe new ignition switch. I am getting tired of throwing stuff at it and have it act up in a week or two again. :mad:

Starting to wonder if there is water in the fuel or air getting in the injection pump some how.

Anyone have any ideas?

[cowboywildbill]

You probably have already tried these things but, Have you tried checking the fuel pressures after the pump. Also is the injector pump good? Or maybe It could be sucking air in the fuel line some where up to the pump. But it sounds like you covered that but I have had large rigs do that and couldn't find any bubbles in the pressure side. I hope you find it. I know it can drive you nuts trying to find the problem. It's probably something simple, but finding it isn't always easy. Also maybe a wire is getting hot and separating in the harness somewhere ? Sorry I couldn't be more helpful Good luck

[a5150nut]

When I got my 94 one of the first things I did was get a can of Contact cleaner and clean all electrical connectors and add dielectric grease to them. Dodged a lot of electrical problems that way. Did go thru several PMD's, set of injectors, fuel solenoid, vacuum control and an injection pump.

Might want to check all electrical grounds. Especially on the right rear head. Bad grounds will run you in circles chasing your tail for days.

[94GMC2500]

I have put a pressure gauge in the drain hose from the filter housing and opened the valve and it has 4 to 5 psi. It will squirt fuel about a foot in the air from the air bleed on top of the filter when opened.

Last year I put new ground wires from engine to body and engine to frame. I have had 3 used and one new pump driver on it. 3 different fuel shut off solenoids, all used though. No idea what shape the injection pump is in.

After I changed the injection pump wire harness it ran the best it ever had for a couple weeks then it started the stalling stuff again.

I am thinking it getting air in the system some how. I was told to put a big shop vac on the filler to the fuel tank to put some pressure in the tank and then check for fuel leaks in fuel lines with soapy water.

[Robyn]

With all that you have been through and replaced my gut feeling is ignition switch.

A poor contact in the switch can kill these quickly

Make sure the ground wire in the PMD harness is connected to the IP as it came factory.

No need to move that ground when you have a remote PMD


Replace the ign switch before you chase your tail on this any more.

12.3 volts at the fuel shut off solenoid is sketchy.


When the rig is running make sure you have 13.5 to 14 volts at each battery and at the power distribution box on the LH fender well (Large + lug)

The battery cables can fail internally in the crimps .

Battery grounds at the battery and the block can and do fail.

The battery cables can look great and be clean on the outside, but can be badly corroded internally.


Poor voltage in the system can drive the ECM nuts and cause all sorts of crap to happen.

Ign switch contacts burn and corrode over time too.

Very well may be that each time you turn things on and off you are disturbing things enough to get a different result.

If the cables are factory/factory type and several years old then they are suspect.

Factory cables use crimped ends where the wire strands are merged with the side terminals

Only soldered ends such as COPPER eyes can be trusted over the long haul.

One other thing... Have you changed the filter harness on the IP ???
This wire harness is near the top rear of the IP and has a little rectangle black box in it.
If these fail all bets are off.

http://r.search.yahoo.com/_ylt=AwrTcXmCZqlZy48A9k6WnIlQ;_ylu=X3oDMTBtdXBkbHJ yBHNlYwNmcC1hdHRyaWIEc2xrA3J1cmw-/RV=2/RE=1504302850/RO=11/RU=http%3a%2f%2fwww.ssdieselsupply.com%2fp62_optic al_sensor_filter_harness.html/RK=1/RS=akPPS5oOJqA2A51JW14Qu33SF30-

Here is a link to a picture of it.

Have you had the PMD wiring harness off of the IP
These can fail at the connections where the wires connect to the IP under the boot.


CHECK IT OUT

Good luck

[94GMC2500]

I replaced the wire harness on the injection pump, I don't think there is that noise filter harness on mine. I am not getting any trouble codes on mine.

The 12.3 volts at the shut off solenoid plug was with truck not running and batteries run down a little from trying to start it.

[Robyn]

Here is a little secret to try.

When it won't start...

Get another rig up alongside (Running) and jump the Drivers side battery and see wassssup.

This will get a full 14 volts to the LH battery and possibly ferret out a voltage issue.

Both batteries are connected, but the LH one feeds the main power box on the rig.

If this gets ya going, then start looking for the source of the low voltage.


The wiring on the engine are very small and a bad connection can really screw things up.
Replacing the complete engine harness is not too tough, just requires the intake be removed

Good luck

[Yukon6.2]

My 98 diesel had a stalling issue that an ignition switch fixed.
My 04 Topkick had a Heater, air conditioning issue that was fixed by replacing the ignition switch.
My neighbor has a 95 GMC gas job that was having transmission issues that were fixed with a new ignition switch.
Pesky little problems

[Robyn]

WE had a GMC Safari that would lose the digital dash, the power seats and power windows plus the tranny would not shift.

All because of the ign switch.

One hot lead had melted the wire, the contact spade and the switch case too.

The GM switches of the era are suspect when they get some time on them.

I would swap out the switch before chasing this gremlin any farther to be on the safe side.

[JohnC]

The dealer overhauled the 4L80E in my '95 twice before I figured out the problem was low voltage to the shift solenoids. By the time they figured out it was the ignition switch, it was off warranty. I told them they bought into the problem when they pulled the trans the first time. They replaced the switch and Bob's my uncle. (Really...) Went another 100K miles before I traded it.

[Robyn]

There are several contacts in the ign switch and depending on which one goes south the issues can be hard on things for sure.

The cost of a switch is minimal.

Our Safari Van had not only trashed the switch, but burnt up the large gang plug on the switch as well.

TRIP TO THE U PULLIT :D

Scarfed up a good one and spliced into the harness...Good to go.


The switch contacts carbon up and then the voltage drops off and the amperage goes through the roof.... next stop things start failing or melting.

[94GMC2500]

I see there is a huge range on prices for ignition switch, would it be best to get a AC delco switch?

[Robyn]

yesssssssssssssssssss

Stay away from the stuff that the aftermarket sells in this case.

Most of the stuff from NAPA is Chinese made junk.

Not sure about Autozone.

A factory Delco switch is gonna be the best bet.

I replaced the AC low pressure cycling switch on the Burb with a Napa switch and it failed before I got home (5 miles)

Some would not even thread on. :eek:

Every replacement failed in about the same interval.

Bought a Delco OEM and its been there over a year now.


Good luck

[JohnC]

I think they quoted me about $380 for mine. The give away was one of the instruments, speedo, I think, didn't work when the trans wasn't shifting. Separate set of contacts for trans and instruments went bad.

[Robyn]

The Van we had was equipped with the digital display, and it would go dark when when the contact failed.

The giveaway was a good thump on the steering wheel would get it going again.

FOR A WHILE

[94GMC2500]

OK another long post, I am starting to think the extension cable to the PMD is bad. I feel like a dope about it. I had trouble getting it started again today, messed with some stuff but didn't really change anything and it started. So I took the 3 extra PMDs I have and tried each one while it would start. Turns out the PMD I grabbed to try when it wouldn't start a few days ago is bad. It would run on the other two, hence that's why I feel like a dope.

So I tried to start it tonight and it ran a little while and it quit again and wouldn't start, so I unplugged the PMD cable by the pump and plugged a PMD that I now know would run up by the pump and it started right up and ran fine.

So I took that PMD back off, plugged the extension cable back in and it would not start again, plugged a extra PMD on the other end of the cable behind the bumper and it started and stalled. So I again unplugged the cable by the pump and plugged the same PMD back in by the pump and it would start right up and ran fine again.

So that makes me think the extension cable is bad. I don't know who made the cable but are these extension cables known for going bad? The cable is only a year old roughly.

[Robyn]

Hmmmmm

Interesting.

Electrical ANYTHING can fail.
A bad solder joint ???? or a bad plug.

Likely not the cable, but more apt to be a connection issue with the plug/s on the cable...

Get a fresh cable from one of the good suppliers and give that a whirl.

The pins are small, and the female end of the extension cable likely has a connector/s that are not making 100% contact.

Trying to tweak those female plugs to get things tightened up is not likely to happen.

I assume you live in Salt country ???

If this is the case that brine tends to aerosol and get into everything.

Corrosion in those tiny connectors wreaks havoc.

Also a tiny bit of Dielectric grease in each female pin hole can do wonders for keeping things working.

No need to slather it on though.

Good find


Best bet is to replace the ext. cable.

Spray the connections with an electrical connector cleaner and let dry, then install.

Electrical

[94GMC2500]

I am in Wisconsin, but don't drive the truck in the winter. I am going to try it with PMD mounted back on the intake manifold without the extension cable to see if the problem stays away. If it does then I will get a new cable.

[DickWells]

This is late, and may not help you at all, given that Robyn has sort of dealt with it. But. Way back in about 03, I was struggling with the PMD issues with my old Sub. 6.5. Was in Florida and she died on me one more time. Bought a new PMD and installed it and only managed to come up with an intermittent problem of the same issues. So, somehow, I managed to probe around that big hermetically sealed block, right above the IP, and found one conductor in there that was on-and-off. I jumped that block with a same size wire and hoped that I hadn't lost some sort of micro chip, capacitor, or resistor, inside, or something. Never had another problem with that PMD, but continued to fight flaky grounds and other issues until I went mechanical. I do seem to recall that I had to actually work hard at flexing that block to make the connection open and close. Forget how many conductors were in there, but it was a good bunch. My wire (IIRC) was purple, with white tracer.

Good luck.

[Robyn]

Good check procedure.

If it stays happy for a while then the gremlin is likely the cable/plugs.


Undo the cable end plugs and inspect the solder joints.

A cracked joint or a cold lap may be all that it is.

Good luck

[94GMC2500]

Truck has not stalled since I put the PMD back on the intake. Pretty sure the problem was in the extension cable.

[Stevediesel]

OK this might get long. I bought this 95 dually a couple years ago. Its had stalling and sometimes not starting problems since I have had it. I have put new fuel tank, new sender, new fuel lines, new lift pump, now wired to run whenever key is on, relocated pump driver and cooler up behind bumper, replaced injection pump wire harness, just put new crank sensor in, replaced fuel shut off on pump, new fuel filter.

Today it started and ran about 10 seconds and quit, and would not restart. First thing I did today was unplug the fuel shut off and checked for voltage with key on, had 12.3 volts, grabbed another shut off solenoid and plugged it in and it worked fine. So I plugged that back together. Then I grabbed a spare pump driver and plugged it in up by the pump, still no start.

So then I took the fuel shut off solenoid out and turned key on and ran some fuel out the hole, put shut off back in and it started, ran rough and quit a couple times but it would restart and then ran fine again. So next I put a piece of clear hose on return out of pump and left it run a long time checking for air, not a bubble. when it does run I can wiggle on wire connections, fuses, relays and cant make it quit. also never get any codes.

It will run a week or two just fine and then the stalling starts up again.

I have no idea what else to do with it. I have another engine wire harness I thought about putting on, or maybe new ignition switch. I am getting tired of throwing stuff at it and have it act up in a week or two again. :mad:

Starting to wonder if there is water in the fuel or air getting in the injection pump some how.

Anyone have any ideas?

It's the oil pressure switch shutting off the lift pump