Engine/Transmission (1994 - 1998) Part time awesome, part time POS - I Need Help!

[Hillbilly_12Valve]

I have a 1994 5.9l 12valve, standard trans, long bed. When it works, I love it! When it acts like a diva, I question my life choices...

Recently it's pulling this, "may or may not start" crap and it's really getting old. I know it hasn't lost fuel prime in 2 days, but I just went out to start it and it will not fire. I cranked it for 30sec, twice and it wouldn't go.

It sat for a year the last time this happened. I had given up, and it sat until the batteries died. I decided to get it going in 25, and bought new batteries last week. When I replaced the batteries I found 2 corroded crimp connectors on the 12v battery cable. One of them broke in 2, that's how I discovered them. After replacing those crimp connectors and the batteries it fired right over. I let it run for 15 minutes to warm up and lubricate since it hadn't run in a year.

Now, 2 days later, I go out to start it this evening and it just cranks over... what could possibly be the reason that it will run one day, and not the next. Then start again a week later without changing anything? Like I said, I'm pretty sure it's not losing fuel prime. I just don't know else to check.

So, please, I need help

 

[Signal73]

Look into the shutoff solenoid. It’s on the side of the injection pump. Make sure it’s lifting up and staying there when you bump the starter.

 

[BigPapa]

Ditto on the Shut-Off Solenoid. There's a Relay in the PDC for the "Hold-up" Circuit labeled "Fuel Pump". It's the same as all the other relays so you can swap them around to test. The Relay for the "Pull-Up Circuit" is on the Firewall next to the relay for the Grid Heaters. You can get a 25-0102 Relay pretty cheap from O'Reilly's that will work. It just doesn't have the hood and bracket. If you find those good, check the boot on the solenoid and if it's torn, just rip it off. It's not needed and will bind it up. If you have to replace the solenoid, you may have to adjust the plunger length. Measure the old one and compare to the new one.

 

[GAmes]

The Relay for the "Pull-Up Circuit" is on the Firewall next to the relay for the Grid Heaters.

Small correction Scott. The other relay on the firewall is for the fuel heater. The grid heater relays are on the fender liner.

Hillbilly, the way to check if you are losing prime is to crack the bleeder bolt on top of the fuel heater housing and then pump the lift pump primer button. If you get raw fuel you have good prime. If you get air then you have an air leak on the suction side of the lift pump.

 

[BigPapa]

Small correction Scott. The other relay on the firewall is for the fuel heater. The grid heater relays are on the fender liner.

Yep, you are correct as usual, Gary. My mistake.

I was thinking "Heater" and my mind immediately went to "Grid Heater". Thanks for the correction.

 

[Hillbilly_12Valve]

So, I pulled the trailer lamp relay and swapped it with the fuel pump relay. It started immediately and I thought problem solved! However, I shut it off and it wouldn't start again...
So I had to have my wife come outside and run the ignition so I could look at the solenoid. When she cranked it the first time it didn't move at all. I stuck my hand in there and gave it some gentle encouragement as she tried it again, and sure enough it fired right up. So I will be buying a shut-off solenoid on my way home from work tomorrow.

Thank you both for pointing me in the right direction!

 

[BigPapa]

You do what you want, but I’d try a new pull-up relat before I bought a new solenoid.

 

[Hillbilly_12Valve]

You do what you want, but I’d try a new pull-up relat before I bought a new solenoid.

I swapped around the relays and it didn't help after the first lucky start... I tried it first with the trailer brake relay and second with the horn relay...

 

[BigPapa]

I’m talking about the relay on the firewall. There’s not another one like it on the truck you can try. See my first post.

 

[GAmes]

I carry a spare. '94-'98 Dodge Cummins Fuel Shutoff Relay

I recommend you remove the solenoid and clean it. They rarely fail but the rubber boot deteriorates and gets jammed on the rod. Clean the bore and plunger, no lube except maybe dry silicone. Before there were new boots available I drove mine without one for several years.

'94-'98 Dodge Cummins Diesel Fuel Shutoff Solenoid Boot

 

[Hillbilly_12Valve]

BigPapa, I misunderstood your first post, I didnt get that the "pull up" and "hold up" relays were different. I will get another 25-0102 relay on my way home and check that first.
I have had a lot going on recently and my brain is not running at 100%.
Thanks again!

 

[GAmes]

There is only a pull up relay. The hold is powered by fuse #9.

 

[BigPapa]

There is only a pull up relay. The hold is powered by fuse #9.

I'll have to disagree on this one, Gary. I had a bad one years ago that I changed.

 

[GAmes]

I believe you are remembering your second truck because mine does not have a fuel pump relay. It does have a fuel system relay but I didn't investigate what it powers. With it removed the engine starts and runs just fine. When I pulled the #9 fuse the solenoid dropped and the engine died.

 

[BigPapa]

I believe you are remembering your second truck

That's very possible now that I think about it, Gary. The '98 I put the '95 12-valve in. The wiring modifications probably used the 24-valve relay.

Not trying to argue, but, that diagram I posted is from a '94 on AllData.

This is the Dodge diagram.

 

[GAmes]

Is the relay in the PDC in a '94, not on the firewall? My PDC looks nothing like that one. If so you may be spot on.

 

[BigPapa]

This is the '97.

 

[BigPapa]

This was my '95.

 

[GAmes]

The diagram is correct but the ASD doesn't power the shut down relay. I pulled mine and once again the engine started and ran.

 

[Hillbilly_12Valve]

So for what it's worth, I brought home a 25-0102 relay, and it doesn't fit my truck... I looked on my firewall and I can't see a relay anywhere. There are 2 additional relays mounted to the driver fender, with the contacts pointed toward the engine and 4 wires attached to each. I have no idea what they are for.
So I have a question then, is the ASD the "hold up" relay? If so which one is the "pull up" relay?
I may have time tomorrow eve to pull the whole solenoid, but I have to go out of town Friday. I won't be able to mess with the truck again until Monday