What a dead horse

[ActionStarCBRxx]

Most common fuel leaks are fuel filter base and lift pump. Check them first and it could be loosing its prime.

I agree with dstang and the other posts about pressurizing the system to check for air. I found with mine that if you open up the top vent (black twisty thing on top of the fuel filter base) and then just turn the truck over till diesel comes out the discharge rubber line. (Process for removing air out the line at the fuel filter base in TM) Then turn the black cap to re-tighten and hop in the cab to start the truck again, that it would start right up. My air leak was in the fuel filter base.

If you cant get the fuel to drain quickly out the line (seconds) then don't keep at it. Pull the lead wire to the IP (pink or purple I dont recall). There is a reference in the TM that dry starting creates a vapor lock.

I also agree that the hot starts is not IP but more likely starter based. Do you have one of the rebuilt gear reduction starters? They tend to not last long when you have starting issues (excessive daily cranking). I ended up going back to the original starter and getting it rebuilt by a good reputable shop.

 

[wayne pick]

Check out Electric fuel pump mod by top prop, as i think you have a fuel delivery problem, a weak or failing mech fuel pump. Also check out, CUCV Spin on filter mod by pawnshop. Stock fuel filter housings are also known to fail. The threads by these guys are informative and complete with instructions and pics. The two mods are wallet friendly compared to chasing down filter and lift pump problems.

 

[tequilaiam]

I had similar problems with hard starts. It did turn out to be the fuel filter base...it was the white sensor (fuel pressure). Here's the thing that had me stuck: it let air in but not fuel out. therefore there was no fuel leak to indicate the problem.

Try this:
remove fuel filter.
pry out that white sensor.
plug the hole at the bottom of that cut-out for the sensor....I used a machine screw and some seal-all but RTV should work. So should JB weld, epoxy or anything else.

If you use a screw or do anything else that may generate shavings...blow out the filter base with WD-40 or something after disconnecting the fuel feed to the IP and return line.



Other tip for chasing down leaks:
Before doing the above, I replaced every fuel line with Tygon tube. It's clear and it's fuel proof. Its not as elastic as regular fuel hose so it can be a pain to slip on the various nipples....a few seconds with a heat gun will make it easier and afterward you don't even need clamps. I bought mine at a local motorcycle shop for $0.99 a foot. Its parts unlimited brand I think.

Anyway, the clear lines really helped identify where the leak was comming from (filter base like others have said). Just that my particular leak was that sensor, not the vent knob or filter element.

 

[tequilaiam]

If you truck fires up then shudders and dies after a few seconds, it's likely air in the line between the fuel filter and IP. You're basically burning the fuel left in the IP and some in the line, then going dry. Continuing to crank will eventually work the air out, which is why the WD-40 trick works.

To eliminate the possibility of your mechanical lift pump being the culprit, try opening the vent knob on the filter base RIGHT AFTER it dies the first time. If your lift pump is good but filter base leaking, you should hear air hissing out of the vent for a second or so as the fuel pressure of the pump still has an air bubble compressed to the same PSI.

To get yourself restarted, with that vent open, pull the pink wire on the injection pump and crank until fuel pees out of the vent. Then close vent, replace wire (this is the procedure in the manual) and try cranking again like normal. It will take a few cranks to get the last bit of air out of the IP but should be doable within 30 seconds of cranking or so. Mashing the gas pedal while cranking (not in the manual) moves the air out faster, I've found.

I also found that a small hole in the fuel fill cap helped with this issue before I found the exact culprit. I observed that ambient air change exaserbated the issue. Basically, my vent cap allowed the cooling air to draw a small vacuum that aggrevated the leaking filter base sensor. The pin hole in the cap eliminted this vacuum and only gravity caused the leak. It was still a PITA but less air got in and I could get it re-started a lot easier after that first shut-down you are experiencing.

Who knows, maybe a small hole in your fuel cap will solve the issue? It all depends on where the air is comming from.

 

[Whitey]

My vote is on the fuel filter. It's probally leaking and letting in air or the fuel begins to drain back to the tank as it sits. At least that's what I have encountered. Good luck and don't give up!

-Whitey

 

[ActionStarCBRxx]

If you truck fires up then shudders and dies after a few seconds, it's likely air in the line between the fuel filter and IP. You're basically burning the fuel left in the IP and some in the line, then going dry. Continuing to crank will eventually work the air out, which is why the WD-40 trick works.

To eliminate the possibility of your mechanical lift pump being the culprit, try opening the vent knob on the filter base RIGHT AFTER it dies the first time. If your lift pump is good but filter base leaking, you should hear air hissing out of the vent for a second or so as the fuel pressure of the pump still has an air bubble compressed to the same PSI.

To get yourself restarted, with that vent open, pull the pink wire on the injection pump and crank until fuel pees out of the vent. Then close vent, replace wire (this is the procedure in the manual) and try cranking again like normal. It will take a few cranks to get the last bit of air out of the IP but should be doable within 30 seconds of cranking or so. Mashing the gas pedal while cranking (not in the manual) moves the air out faster, I've found.

I also found that a small hole in the fuel fill cap helped with this issue before I found the exact culprit. I observed that ambient air change exaserbated the issue. Basically, my vent cap allowed the cooling air to draw a small vacuum that aggrevated the leaking filter base sensor. The pin hole in the cap eliminted this vacuum and only gravity caused the leak. It was still a PITA but less air got in and I could get it re-started a lot easier after that first shut-down you are experiencing.

Who knows, maybe a small hole in your fuel cap will solve the issue? It all depends on where the air is comming from.

Now thats good advice. I read a lot trying to diagnose mine when it happened and missed that tidbit.

 

[top_prop]

Wow... great thread going here.

I've got similar trouble with my CUCV... hard starts if it sits for days. My truck always fires up fast unless its been sitting a good while. And it roars to life if its hot.

While underneath it working on other stuff. I've noticed fuel dripping out of the water in fuel drain line, but haven't trouble shot it beyond that. I suspect it's getting air at the filter. I've got an electric pump (which I posted how I did the mod at: http://www.steelsoldiers.com/cucv/48444-electric-fuel-pump-install.html )

I've read in the hanyes diesel tech manual that the oring for the water in fuel drain tends to go bad and has a special replacement but haven't been able to locate one. And I'm not even sure its that and not the fuel press sensor... While I may trouble shoot this, if I find the source as being int he standadyne 80 base, i'll probably just replace it with a spin on. I've got a spin on base on my 6.2 suburban... I'm thinking I'll just swap in a the same base and only need to stock on type of replacemetn fuel fiter.

Though I've got an old ford spin on type that uses different filters that has a scrader valve for bleading the system... the base on my suburban requires you to crack the filter until fuel runs out to blead it....

i guess I'm getting long winded... so I'll get back on topic: Iluvbudwsr, I'd reccommend the electric pump mod as a first step... you can then trouble shoot for an air leak. Find the leak with pressure and not have to mess with tricks to pressurize the fuel tank as posted above. And make priming after a filter change easy.

Tom

 

[Hasdrubal]

I also had the dreaded leaking fuel pressure sensor syndrome. Couldn't see any fuel leaking, so like tequilaiam I drilled a small hole in the fuel cap. That fixed the problem for a few years but then I started to need a few seconds cranking to start. That was finally fixed when I installed a new fuel filter base. Fires on first crank now.