Question on IP fuel return & No start

[ZZ4x4]

Hey all,
I've installed a donor 6.2 into my HMMWV and I'm having one heck of a hard time getting it to start. The wait to start light comes on for the right amount of time. It will crank for several minutes ( 20 secs at a time) with not so much of a kick. Then it may slowly fire a cyl or two , catch, and run for 2 seconds max and then die. Then it's another couple minutes of cranking with nothing.

Just FYI the entire fuel and glow plug systems are new.

• New Fuel tank and lines
• Fresh Diesel
• New rebuilt injector pump from reputable company
• New engine wiring harness
• New digital Smart Start controller and temp sensor
• New Fuel filter

I've done the following things:

• Compression check in all cylinders. All good
• Glow plug resistance checked. All are 1.6 ohm
• Glow plugs are getting 24V when wait light is on.
• Injector pump shutoff solenoid is getting 24 V. Can hear click of injector pump solenoid.
• Fuel weeps from all injector lines when cracked
• Fuel weeps from filter bleed screw when cracked
• Added extra ground to block.

It sure seems like she is fuel starved but the IP is full of fuel with extra fuel rising out of the IP return hose. Does the mech fuel pressure affect performance? I was under the impression the lift pump in the IP doesn't care about input pressure as long as there is fuel.

I installed a clear fuel return line on the top of the injector pump. I get a little bit of fuel which slowly rises into the line and trickles out. Not a huge flow. I do still get some bubbles in this line. The bubbles and very low flow concerns me. Does anyone know if the small amount of flow is normal or should I be seeing a large flow? I read one HMMWV manual instructing the driver of a run-away engine to pinch that hose to shut the engine. How would that stop the engine when the fuel is still being pumped into the IP from the other end. It would just build a little more fuel pressure in the IP. Nevertheless I'm leaning towards a mech fuel pump problem. Any confirmation or ideas?

Should I play with the timing?
Thanks,
Jeff

 

[cpf240]

If the return line, or its check valve, is blocked, or pinched as in the TM, it will create back pressure which will keep it from running.

 

[ZZ4x4]

If the return line, or its check valve, is blocked, or pinched as in the TM, it will create back pressure which will keep it from running.

Yeah. Just seems odd.

Anyway, another update. The bubbles seem to be clearing up and I now installed a pressure gauge on the top of the fuel filter canister. I'm getting 8 PSI of fuel pressure at the canister ( which is high since the TM says 3 PSI) but still low flow through the IP. When I pulled the factory STE/ ICE pressure sensor there was a lot of fuel pressure built up in there. Sprayed fuel everywhere. Is that normal? I wonder if there is some restriction in the new IP. I'm trying to Keep it Simple and not going off on goose chases but this has me scratching my head.

 

[ZZ4x4]

Another update:
I talked to the IP repair house and they said the flow rate through the IP and out of the return port is set by them. The lowish flow is normal. They use 5psi fuel pressure when setting it up and the 8psi I am seeing should be fine. They suggested advancing timing by 1/8" which I tried. Still no joy.

 

[Retiredwarhorses]

If you pull a Glow plug, is it wet with fuel? If it is, I suspect your not getting voltage to your Glow plugs.
as you stated, try advancing the IJ pump, turn toward driver side...make sure whoever put in the IJ pump that the stud went in the Oval hole and Not the round hole....common mistake....you can take the oil filler off and rotate fan to see what hole was used.

 

[ZZ4x4]

If you pull a Glow plug, is it wet with fuel? If it is, I suspect your not getting voltage to your Glow plugs.
as you stated, try advancing the IJ pump, turn toward driver side...make sure whoever put in the IJ pump that the stud went in the Oval hole and Not the round hole....common mistake....you can take the oil filler off and rotate fan to see what hole was used.

Thanks for the info. I'm the one who installed the IP ( the old one developed a huge leak). I did install with the pin in the oval hole ( and verified yesterday). My glowplugs do heat ( actually pulled one right after cycling and it smoked when I touched it to my glove). I then unplugged one glow plug, cranked for 20 seconds and pulled the plug. It was dry as a bone. Then I cranked with no plug installed and there is no fuel mist coming out of the hole. This confirms there is just no fuel making it into the cylinders. Keep in mind there IS fuel at the injectors when I crack the lines. Seems like it has to be one of two things 1) The IP is not making sufficient pressure to push fuel past the injector spring load or 2) all injectors are clogged. Number 2 seems less likely to me since the engine has started a few times and run for a couple seconds before dying. If the injectors where THAT clogged I don't think it would have started at all. I talked to the IP rebuilder and they are going to send out another under warranty. I guess I'll be pulling the IP again to replace it with another rebuild. What a pain!

 

[R Racing]

Not familiar with the HMMWV. But on the 5 tons it's a suction system. And if we get a loose fitting or a hose with a small hole or dry rot . They do the exact same thing. Just thought I'd put that out there.

 

[Retiredwarhorses]

I would pull the injectors and have them pop tested as well, also install new drain back lines.
I have had my fair share of rubuilt pumps, both mil and civ that have failed. So yes...another pump is warrnanted...assuming you have fully bled the fuel system....some are much harder then others.

 

[Retiredwarhorses]

Oh...did it run fine with the leaky pump?

 

[ZZ4x4]

Oh...did it run fine with the leaky pump?

It is an engine from a donor vehicle and I never got it to start with the old leaking IP, but I determined the PCB was bad and had no operational glowplugs at that time. I replaced both the IP and glowplug controller at the same time. The glowplugs are working fine now. We'll see what happens with another IP.

 

[TedG]

After you do what Steve said, try blowing air in to the return line from outlet of IP. Remove fuel cap and then blow air (low pressure) into the return line. If you don't hear air escaping out the tank, then you have a blockage in the return line. Replace the lines since it is easy and inexpensive.

Also, make sure your batteries are fully charged and you use a booster. Low voltage can cause the IP not to engage and it can toast your pcb. Make sure you have the grounding harness installed as well.

 

[ZZ4x4]

Thanks for the suggestions Ted. I did blow into the return line at the IP ( I know diesel is not tasty) and I hear the bubbles in the fuel tank so I think it is clear. The batteries are new and the engine cranks fast until I run the run the batteries down trying to start. I do recharge them at night for the next day's fun
I did try one other thing yesterday and replaced one injector from another engine and cranked for a while without operating the glowplug. Still had a dry glowplug in that cylinder so this points to a bad IP still ( or a whole slew of bad injectors in my shop). Everything is taken apart now waiting for the IP. Will keep you posted.

 

[TedG]

Did you have fuel in the "bowl" of the ip? Did you hear a click inside the ip when you switch power on? Also, the check valve on the outlet of the ip can stick shut from gumming diesel. Hopefully the ip shop can tell you if really needed to be rebuilt and what the problem is/was. Regardless, a rebuilt ip makes a big difference in the under powered hmmwv.

 

[ZZ4x4]

Yes, the IP was full of fuel and I did hear the clicks of the fuel and cold advance solenoids. Also, I swapped the check valve with other IP cores I have laying around. I even tried running with no IP check valve and dumping into a bottle. Nothing helped. The new IP is due in tomorrow. Might be Saturday before I can get it installed. Fingers crossed.

 

[ZZ4x4]

OK, all fixed. For the archives I replaced the IP with another and she fired right up. All is good.

Lessons learned:
-Even though the IP was rebuilt by a reputable company and it was "thoroughly bench tested" it still had major problems. At least the company did right and provided another immediately and covered shipping cost.
-Even though I had fuel at all of the injectors and return flow, the IP was still bad.
-The return flow should be pretty high. I was getting flow but very little ( like a dripping). The issue could still have been some kind of restriction in the return flow. Even with the check valve not installed the flow was minimal.

Hope it helps someone in the future.
Jeff