Won't start. Ideas needed-Please take a look

[restoguy]

I have searched until my eyes burned and didn't find anyone with the same symptoms I have, so here goes.
First a little back ground.
I had a fuel leak around the filter housing. It would cause the fuel lines to pick up air and lose pressure. In order to get it to start without burning up the starter and batteries I would have to jump the lift pump relay before cranking the engine. This worked fine for the last couple weeks until I had time to fix it(I don't drive it much lately). So today I pulled the fuel filter housing out of the rig and cleaned it up. I replace the O-rings on the heater and water sensor and put the filter back in. I jumped the LP and bled the air out of the filter housing. I knew that the line between the filter and IP probably had some air in it, but figured what the heck, it would work it's way out. I've had this pickup('94 K2500 w/4L80E) for 5 years now and I've replaced the fuel filter numerous times.(Not to mention the whole engine 3 times and an injection pump once!) So I've 'been down this road' so to speak. I cranked the engine and it fired right up, ran for about 5-10 seconds and then died. This was to be expected. I cranked and cranked again and got nothing. I figured that I had air locked the pump so I loosened an injector line to bleed the pump. I cranked again and it tried to start then died. Assuming that I had bled enough of the air out I closed the line and tried to start the truck. Again, it would not start, nor even try to. I opened three lines this time and when I cranked it I got no fuel or air at the injectors. I have checked to see that I have fuel being pressure fed to the IP, the fuel shut-off solenoid is operating correctly, and I have some fuel flowing through the retrun. I have checked numerous times to verify that there is no air at the filter housing. With an injector line completely removed from the injector I don't get so much as a drip of fuel when the engine is cranked over. I know, you're thinking "PMD". Well, I have two on the truck. One mounted on a cooler and one on the pump. Both were known to be good with in the last week. The truck drove into the shop on one PMD and the other was just used a week or so ago when the truck stalled. The stall was later found to be air in the line and not PMD related. I have tried both PMD's and neither produces any better result. The pump is not metering fuel for some reason. I can discount the PMD, but can not find the problem. Anybody have any thoughts?

P.S. I have cranked the engine enough in my attempts to fix this problem to be equivelent to about 6000 miles of driving! So I do not believe that there is any air in the system causing this problem. I believe it's a pump problem, but I don't know where to start short of pulling the pump. Thanks for your help, ahead of time!

[More Power]

It's likely just a nasty airlock. I had this happen on a 1994 6.5 I owned as well.

Instead of grinding away at the starter for more than 3-4 attempts to get fuel to appear at an injector line, I removed the center/front bolt on top of the intake plenum. I then dribbled about 1/2 to 3/4 teaspoon of clean diesel fuel into that hole. The raw fuel will find its way into a couple or three of the cylinders.

Then, I cranked again. The engine will smoke and miss, as it fires on the few cylinders, and it'll spin a lot faster with the help of that fuel than the engine will spin when using just the starter. Two or three sessions like that solved my problem.

By the way, don't crank for more than 20 seconds at a time, and let the starter cool for 2-3 minutes in between cranking sessions.

In the 1992-95 models, the fuel lift pump relay will activate while rotating the ignition key to the crank position. You shouldn't have to hot-wire the lift pump.

Jim

[restoguy]

Thanks, MP, I'll be trying that first thing in the morning. I only jumped the LP to ensure that it's doing what I expect. Just to take one variable out of the equation while trying to solve this puzzle.

[More Power]

Judiciously using raw fuel to help solve an airlock was discovered back in the 80's when I took my 6.2 K1500 wheeling. I had about a half tank of fuel, which allowed air to find its way into the fuel tank pickup when the truck was at a steep angle. After about 5-10 minutes of running, the engine stalled. I was able to coast to a flat spot, and then begin the process of figuring out what to do.

We were a long way from help, and I dumbly didn't have any tools with me - I'd only owned this truck (my first diesel) for a few months. My brother-in-law suggested using fuel to prime the engine. Using a vacuum hose, I siphoned some fuel out of the tank, dribbled a small amount of fuel into the intake, and then cranked. Not counting the first 4-5 cranking sessions without the extra fuel, it took another 2-3 cranking sessions with the dribbled-in fuel to get it running. This saved the day... and a long walk back... ;)

Since then, I've used this trick to help start a couple other airlocked diesels. As long as you don't use enough fuel to create a hydraulic lock, you'll be OK. A teaspoon or less should be fine, even if it all went into one cyl.

Jim

[restoguy]

Thanks for the help, MP. I used this trick today to help the batteries along. I'll be putting it in the ole 'toolbox' so to speak. Right beside using a hair dryer or heat gun to start one when the weather's cold and the glows aren't up to the job! I found out, however, that the problem was electrical in nature. My friend, who's shop the truck was at, showed up to work before I got there and messed around with it for an hour or so. Just before I got there he decided to switch PMD's again and when he unplugged the connector from the PMD on the cooler he noticed that one of the contactors had been pushed back inside it's hole and wasn't making connection with the pin on the PMD. We fooled with it for about 45min before getting it back into the correct possition, but when we did we only had to crank a couple revs before fuel started showing up around the injector nuts. A couple more revs and the engine was running! So I tightened up the nuts, and cleaned up the mess. Now it's back on the road and, as far as I can tell, doesn't leak diesel anymore. Maybe my trouble will help someone else in the future.