LJ78: 2L-T Runs then Stops suddenly Post Diesel Injector Service and Glow Plug Change - Troubleshooting - Solved (1 Viewer)

[tiresandals]

After doing some fuel system work I was driving my LJ78 and it just stopped. Enough fuel. Injectors are dialed in and getting fuel. I don't think that was the issue. So I looked a little more closely.

I found that a fusible link was burnt out. The link ran to the glowplug relay (orange arrow). I found that the glowplugs I had installed were slightly shorter (my 1/8th inch or so) and allowed the glowplug strap to short against the metal diesel return system (blue arrow).

I replaced the portion of the fusible link that was blown and adjusted the strap so that there was no longer a short. I checked again to make sure it was getting fuel and the battery had a full charge. It still wouldn't start.

Then I replaced the glowplugs with new ones and it started immediately. I let the engine idle for several minutes. Then it stopped and won't start again (exactly as before). This is about the same length of time that it ran before stopping last time. Clearly I found and fixed part of the problem, but something else is still going on... I have a sense that there is some additional short or something that is causing the glowplugs to malfunction. I checked the clearance and connection on the glowplug strap. Its in a good position, clear of any grounding metal.

I checked the glowplugs that I removed and they all test about 1 - 2 ohms. I think this means they are good.

I'd appreciate your advise troubleshooting this problem.

 

[tiresandals]

Some resolution...

GTSSportCoupe pointed out that he had a nasty short LJ78 | Electrical Short - https://forum.ih8mud.com/threads/lj78-electrical-short.1324157/post-15193734​

Consulting the shop manual I see the problem. It doesn't really show the order to reinstall the glow rail.

So I used a wire brush and cleaned all the connections and then put the glow rail on before the wiring. The LC starts right up again. I think the issue was a poor connection that wasn't allowing the glowplugs to get enough juice. There was a connection according to the volt meter, but not a good enough connection to carry the ridiculous amps required to glow the plugs.

We'll see if this fixes it for good.

 

[AirheadNut]

Not sure what would cause the engine to fail to start just after running for several minutes, but the glow plugs not working would not be the problem. If the engine had run for several minutes it should be able to start just fine with no glow plugs. I think you're on to something with an electrical short.

 

[tiresandals]

Not sure what would cause the engine to fail to start just after running for several minutes, but the glow plugs not working would not be the problem. If the engine had run for several minutes it should be able to start just fine with no glow plugs. I think you're on to something with an electrical short.

I think you are right. I noticed some fuel leaking around the first injector. Today I’m going to replace the injector and see if that fixes the problem.

I think this was a combination issue, both a leaky injector and loose connection to the glow plugs.

 

[JDM Journeys]

Was there any accompanying white smoke when it stalled?

 

[tiresandals]

Was there any accompanying white smoke when it stalled?

Yes, when it was running for a few minutes it was puffing quite a bit of smoke the whole time. I thought this was odd. In the past, it would puff a bit then clear up.

 

[JDM Journeys]

Yes, when it was running for a few minutes it was puffing quite a bit of smoke the whole time. I thought this was odd. In the past, it would puff a bit then clear up.

If the glow system is compromised then I'd expect rough running and white smoke until warmup but stalling out entirely after running is something else... As Airhead said, you don't need glow to run. Given the leaking injector, I'd suspect air in the fuel system. Might be time for the clear fuel line? We all end up here eventually. LOL. If you're not familiar, many of us have done it...

 

[tiresandals]

1hz fuel issue - https://forum.ih8mud.com/threads/1hz-fuel-issue.1313753/post-14985821 got it! I'll give that a try.

 

[tiresandals]

The clear fuel line is a great diagnostic tool. I replaced a return fuel line that looked old. That helped, but I could still see bubbles. Then I tightened the nut on the fuel return bar that goes from injector to injector. That took care of the leak. Then I tightened the fuel supply line to the first infector. That got rid of the last of the bubbles.

Next I'll run it for a while and check for white smoke. As I understand it, that points to air in the fuel line.

Thank you everyone for your help. I hope my experience and these photographs will be helpful to others who may run into the same trouble.

 

[JDM Journeys]

Yep - white smoke is typically either unburnt fuel (incomplete combustion on cold start/ low compression / retarded timing) or air in fuel. Sounds like you nailed it!

I ended up replacing all my rubber lines/filter housing/primer by the time I was done, as well as the pickup at the tank. But once the air is banished? Happy days!

 

[tiresandals]

Thanks! Just drove it down to fill up the tank. No white smoke. I agree about the hoses. It’s 30 years old. The rubber is tired and should be replaced.

when I had the injectors out I cleaned them and checked the release pressure, the spray pattern improved but still wasn’t great. I wonder is should remove the fuel pump and injectors and send them in to be served. I’m at 280k KM.

 

[JDM Journeys]

Thanks! Just drove it down to fill up the tank. No white smoke. I agree about the hoses. It’s 30 years old. The rubber is tired and should be replaced.

when I had the injectors out I cleaned them and checked the release pressure, the spray pattern improved but still wasn’t great. I wonder is should remove the fuel pump and injectors and send them in to be served. I’m at 280k KM.

Excellent work!

That's a lot of k's if all original. When I replaced my injectors and had pump done (1hz) it wasn't dramatic but definitely saw lower EGT's, better acceleration and the black smoke all but disappeared.