another update on my engine swap. engine starts and dies 5 minutes later.

Sooo.

I have the newer engine in my truck now. I have gotten it to fire up (after I had to swap the lift pump out) and it will run for 3-5 minutes and then die on me and I cannot get it restarted until I re purge the system. I'll re purge the fuel filter first even though when I open up the top petcock fuel comes out under pressure. Then I'll take out all the glow plugs and crank the engine until fuel mist comes out of all the glow plug holes. I'll put the plugs back in and it will fire right up on the first try like normal. It will run great for about 3-5 minutes and then die and I cannot restart it until I repurge, as there will be no fuel getting to the injectors no matter how long I crank it for.

Now I know your first instinct would be to look at the injection pump. That’s what I did. The pump that came with the engine was leaking from the bottom of the pump housing from one of the bolts so I thought maybe it was sucking in air too. I replaced it yesterday with the recently rebuilt one from my bad engine. (It has only 3000 miles on it that I put on it myself) When I try to start the truck I still have the same problem.

I've gone back and re tightened all the hose clamps on all the rubber lines to no avail. The only thing I can guess is that the fuel filter base may be letting in air and once the bubble gets sucked into the pump it quits. The fuel filter and filter base assembly were bumped a couple of times (not hard) when the engine was put in. But I have eliminated everything else.

Also I think I have eliminated any possibility of electrical problems by testing the voltage of the pink fuel shut off solenoid wire the last time it died on me and found that it was getting 12v. The advance solenoid and high idle leads (the green ones) had no voltage not even when I recycled the ignition. Could this be to problem?

So I guess it comes down to two possibilities. Either it’s the fuel filter base that is leaking or it has something to do with the green advance/high idle leads having no voltage.

Since if I remember right the high idle solenoid will be energized along with the advance solenoid before the engine is even cranked. They must be working when the engine does successfully turn over but I haven’t verified that other than through the fact that the high idle solenoid does function correctly when the engine dose crank over.

If it is an electrical issue where can I look for a continuity issue? The schematics are a pain to work through.
Thanks

just for S & G did check your fuel check valve??

could the lift pump or any of its fittings be letting air into the fuel supply ...somewhere between the fuel tank and the injection pump?

sounds like the injection pump works when it has fuel to inject

the lift pump is a good 18mo old one off my blown motor.

Is the fuel check valve the one with the glass bead in it on the injection pump? If so its clear.

The fast idle and advance solenoids only have power when the engine is cold. Sounds like you have a restriction somewhere in the fuel line. Glad to hear you're making progress.

except that the engine is still cold enough for the glow plugs to come on and there is still no voltage at the timing advance or fast idle connectors when the engine dies even though the fuel shut off solinoid is still engergized.

m1garand_man said:

except that the engine is still cold enough for the glow plugs to come on and there is still no voltage at the timing advance or fast idle connectors when the engine dies even though the fuel shut off solinoid is still engergized.

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FWIW, I have a 91 Suburban with a 6.2 and the fast idle and cold timing advance has been disco'ed for years with no ill effect.

Sounds like its running on the fuel in the IP as it runs out it dies your not getting fuel to the IP to keep it full all the time.

Get a 5 gallon can of diesel and hook this to your fuel pump. If it runs for more than five minutes, you may have an air getting in between the pump and tank. Maybe bypass the fuel filter also to see if its getting air from there also.

Could you have a check valve in the lift pump sticking, working when you prime but sticking with rpm, this thought is from a 5t owner who knows almost nothing about cucvs

I like the 5 gal can idea! come off the lift pump pickup into fuel can purge and see if it runs on, if so find your leaking between tank and pump! your sucking air somewhere! all it takes is a loose connection when you crank it pumps fuel when it starts the suction is a bit better and will suck air into a loose connection or a bad hose!

Yes, and if this doesn't work you may need to tee in a pressure gauge to make sure your new pump is pumping. I know it was mentioned before, you did get the pushrod lined up right?

m1garand_man said:

except that the engine is still cold enough for the glow plugs to come on and there is still no voltage at the timing advance or fast idle connectors when the engine dies even though the fuel shut off solinoid is still engergized.

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The engine could be warm enough to have shut off the advance and fast idle solenoids. They are on a separate temperature switch. When the engine has sat overnight check to see if they have power before you start the engine. You should be able to tell when they turn off by the engine speed and sound.

Well here’s some new info. So I bypassed the sensor today and the truck ran great with no problems until I turned it off my self about 15 minutes later. In that time the thermostat even opened. So it seems like I have made progress. The truck started up with no problems on the first time, which tells me there is no problem with air getting in the fuel.

I checked resistance of the senor out when the truck was cold before starting it and I got .5 ohms when the truck was up to operating temp I got zero continuity. To confirm my suspicions that the senor is bad I reattached the connectors to the sensor while the engine was hot and couldn’t get it to turn over. Once I put the jumper back in the connectors the truck started up fine first try. Also while running I pulled the timing advance solenoid connector and it did kill the engine. So I'm 99% sure that when I change the current sensor over with the one that is on my old engine that things will be fine.

my only other question is why is there no continuity in the temperature sensor when it is hot? I am guessing this is how the timing advance and the fast idle shuts off but why does that kill the fuel flow in both of my injection pumps?

I guess I'll know tomorrow when I put my other sensor in tomorrow and I'll see if I have an answer.

Anything new

Curious did you get humvee take out, and if did, did you swap the fuel solenoids??

You don't have the idle and cutoff wiring reversed on the pump by chance?

mistaken1 said:

You don't have the idle and cutoff wiring reversed on the pump by chance?

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That did occure to me and I verified that I dont have it reversed. In fact you cannot fit the green connectors on the fuel cut off solinoid contact since it is too large

I did not think you could reverse the connectors but not knowing where you got your truck a previous owner could have engineered them to reverse.

If I understand you correctly, that the engine runs until that cold advance de-energizes, sure sounds like it is reversed.

Is it possible the circuits are reversed in the wiring harness?

Does the shut off circuit still have power after the advance circuit cuts off the engine?

If it was your original engine I would wonder if the IP timing marks were lined up or if the timing chain had stretched\jumped. IOW is the IP timing off such that the advance is needed to make the engine run.

Something is not right, I wish I could be more help.