No start. Cold or ??

[JTodd]

After bragging about my Sub's reliability and ability to withstand the cold a problem has come up. Driving home on Thursday while in moderate traffic it hesitated a couple times. Pulled to the right lane in case it died, but nothing more. I caulked it to the cold - it was -10*F. I plugged it in over night and in the morning (-13*) it started right up. I backed it up and closer to the porch to let it warm up before loading the kids in. Went out to leave, and it was not running.

Worked on different things over the last two days including a new fuel filter, two new batteries (testing shows they were bad), fuel conditioner (supposed to thaw jelled diesel) and 5 gallons of fuel. It is in the low 20s today and still nothing, except for a brief start first thing this morning. I left it plugged in all night and a battery charger on it. I let it glow and cranked it. It fired up and ran smoothly for about 20 seconds. Once it died, nothing close to a restart.

Whenever the key is turned on, I hear the 'rattle' of the lift pump. It does sound a bit louder than normal, and when I replaced the filter the bowl was nearly dry. I filled it before putting the new filter in. However, when I open the purge, no fuel comes out.

The last thing that is pretty perplexing is that even with new 770 cranking amp batteries, it cranks fine at first but slows pretty quickly. If I were to crank it for a full 15 seconds, it would almost be to the 'wuw-wuw-wuw' of a dead battery. I have tried to squirt wd-40 in, but I am not sure where to squirt. I tried to squirt right at the intake of the turbo, but am not sure if it got in. I know that it made no difference.

[DmaxMaverick]

Sounds like your standard issue OPS failure (Oil Pressure Switch). Lift pump runs with key cycle before engine start, then no fuel after the engine runs for a bit. Really cold temps and thick fuel doesn't help matters, but it doesn't matter if the LP isn't doing its job. It sounds like the LP is working, or it wouldn't start the first time. Your empty filter bowl when you changed it, and no fuel flow while running are pretty good indicators. Could be the switch itself, or associated wiring.

[JTodd]

After cranking and the key returned to off, the LP continues to run for a short time (4-5 seconds). If the OPS was bad, wouldn't it kill the LP right away? Where is the OPS anyway? I know it is at the back of the engine, but I don't know what I am looking for. Is there a way to bypass it to test?

[JTodd]

Update:

It just was not getting fuel. The LP was much louder than normal, so I surmised it was cavitating. I searched through the site to figure out how to bypass the normal state of the LP shutting off. I tried jumping to the female spade connector at the driver's side hood hinge, but got nothing. Then I found the trick of putting the truck in gear (R or D) and turning it to run. Pump kept running until I noticed a distinct sound change. It was finally pumping more than air. Once fuel came out of the filter drain I tried to start it. It tried for 10 seconds of cranking or so as the air purged out and it fired.

Once running, it idles smoothly. Shut it down for a bit an restarted without issue. Something went wrong initially, which I am going to blame on bad fuel that started to jell, and from there on I was chasing symptoms.

Glad to get that done.