Question about Fuel Delivery to Injection Pump

[Tanabi]

Hey there;

I've been trying to diagnose some fuel problems with my HMMWV and I have a question that haven't been able to find an answer to.

The vendor who rebuilt my Injector Pump asked me to gravity-feed some diesel in from a fuel can straight to the pump to diagnose why their rebuilt IP isn't working (that's another story).

I put the old fuel intake line that goes from the fuel filter to the IP into a mason jar, and while I was cranking it, I noticed that the fuel comes in spurts. It gushes, then nothing, gushes, then nothing. The spurts are very regular and even, and the fuel coming into the jar is really clean.

My question is, is this normal? I would have expected the fuel to come as a steady stream from the filter rather than in these pulses. I read the tech manual and I can't see anything about this specifically, nor are my searches turning up anything, but I think I may be searching for the wrong thing.

Thanks!

 

[jkcondrey]

Have you checked the fuel at the port off the filter canister to verify the spurting there? In the driver wheel well, on the vertical panel should be a hose going to a petcock. Open it while running or cranking to check for water, etc and you can possibly confirm the spurting. Have you also changed your fuel filter, pump etc, recently? There is an old vhs recording on diagnosing fuel issues on youtube. I used it after I picked mine up. Search "fuel issue hmmwv" on youtube.

 

[Tanabi]

Have you checked the fuel at the port off the filter canister to verify the spurting there? In the driver wheel well, on the vertical panel should be a hose going to a petcock. Open it while running or cranking to check for water, etc and you can possibly confirm the spurting. Have you also changed your fuel filter, pump etc, recently? There is an old vhs recording on diagnosing fuel issues on youtube. I used it after I picked mine up. Search "fuel issue hmmwv" on youtube.

I haven't checked that port, I will do so. My fuel filter I changed maybe 3 or 4 months ago. I've seen that video, and it shows the fuel coming out as a constant stream from that valve so I'll give that a try and see what happens. If its pulsing there, too, then I think I likely have a problem. I haven't seen any info on how it comes out on the IP end, though.

 

[papakb]

The way the fuel system works in the HMMWV is that the fuel pump (also called the lift pump) in the lower right front side of the engine pulls the fuel from the tank and pushes it up to the water separator filter mounted on the firewall behind the left rear of the engine. From there it goes to the IP and gets injected into the engine. When the engine is cranking over the fuel will spurt as the fuel pump cycles. When the engine is running it will be a continuous flow.

 

[Tanabi]

The way the fuel system works in the HMMWV is that the fuel pump (also called the lift pump) in the lower right front side of the engine pulls the fuel from the tank and pushes it up to the water separator filter mounted on the firewall behind the left rear of the engine. From there it goes to the IP and gets injected into the engine. When the engine is cranking over the fuel will spurt as the fuel pump cycles. When the engine is running it will be a continuous flow.

Thank you, this answers my question perfectly!

 

[wpy2080]

Tanabi, keep us posted on the IP issue. I am going through the same thing right now with a fuel delivery problem... They will ruin your week with these trucks. I had my IP rebuilt last year and this spring the HMMWV (1993 - M99 just died as I was driving down the road... I took a video of the pulsing fuel from the filter and showed it to a HMMWV mechanic. He also stated that was normal when the vehicle is cranking and not running. He also stated that you can get false positives with that test because the mechanical lift pump can show good fuel delivery to the IP but can also cause the system to lose prime if the diaphragm (check valve) is malfunctioning. The manual feed test to the IP should tell you if the problem is pre IP. (Pre IP issues are almost always air leaks in the lines or fuel filter, pickup tube obstructions from the tank or mechanical lift pump failure.) I am to the point that I am going to pull my tank, clean it, replace rubber lines and mechanical lift pump... All good to do anyway for life of your truck... The next issue on the pump itself could be the shutoff solenoid (electoral tests in TM for that but a bad PCB or EESS could also case the shutoff solenoid malfunction) The other issue you could check on the IP itself is the return line check valve (the short rubber hose on front of IP runs off of this valve and can be removed and cleaned with carb cleaner. Guys on this forum have had bad solenoids and check valves that have caused major issues and these can be replaced without taking out the IP...Good luck, keep us posted.

 

[Milcommoguy]

All good points as I read them. Might just loosen one of the injectors fuel feed lines (the easy one) at the injector and see if fuel is showing up there when cranking. Won't be a lot, but should fill a thimble after a few tries. It would be an "end to end" test and easy to do. I know you stated some fuel pulsing / pressure? / flow on the output side of the filter. My thinking something is missing from filter to the end of the line?


EASY CHECK > Check for 24 VDC at the IP solenoid (on top forward wire of harness connection) in the run position. A better electrical test would be to measure the current. Typical solenoid for this application is 24 ohms. So "E/I.R" Ohms law works out to about 1 amp. That would be normal in the ball park of a good solenoid.

The "CLICKING TEST" works too. > In RUN position remove and reconnect wire above and at same time listen for a slight "tic" or 'click' of the solenoid energizing. May have to do it a few tries to get the hang of it. Good electrical test without fancy multi-meter.

Good so far BUT, doesn't mean that the linkage is engaging. That's another issue inside the IP...OR "place open ended flow chart here"

Be mindful of wiring being swapped with cold start solenoid, just to the rear. Wouldn't be the first time.

Note that there is a filter "inlet filter" on the back of the pump. IF a bunch of JUNK made it there over time it could be clogged. I have seen engines start and run and then loose power... smoke, stall out, die, stop, start then stop due to this filter leading to a rebuild rather than a two dollar filter.

Lots of info on the Google. Easy Stanadyne pump here > http://www.trucktrend.com/how-to/expert-advice/0809dp-stanadyne-db2-injection-pump/
to factory manuals.

AIR - FUEL - SPIN and go. Good luck.

CAM

 

[papakb]

The wire you want to check is the #54 lead on the top of the IP.

 

[Tanabi]

So the problem that I originally had is one day the HMMWV wouldn't start -- it was actually my daily driver, so I drove it every day. Up to that point, it started having some trouble getting started in the morning... I would describe it as "lazy", almost like I was trying to get it to start in the cold even though ambient temperature was around 70. It would start, but it needed more cranking than I'd expect.

Then one day it wouldn't start at all. I cracked open the fuel injectors, no fuel. Opened the return line at the top of the IP, no fuel. Pulled the supply line, and got the pulses of gushed fuel as described at the start of the post. I sent the IP for a rebuild to a shop that sells the service on ebay, and had a 100% positive rating.

I get the IP back, it looks absolutely beautiful. I put it back in the truck, get everything back together...

EXACT same problem.

I tried gravity-feeding fuel directly to the IP from a fuel can, still no joy.

I called the company that rebuilt it, and they said they have records of it testing correctly. So either I'm crazy/did something wrong or they're lying to me. This is a pretty simple piece of hardware so I doubt I did something wrong installing it. They are really hard to get in touch with and don't return calls -- basically if I don't get them on the phone when I call, I don't hear back -- so this has been a really slow process working with them to diagnose the problem.

Anyway, I'll look at the links you guys sent me, but I'm sort of inclined to tow it to a diesel shop at this point. Much as I like being a do-it-myselfer, I really just want my truck to roll again

 

[Action]

probably not related, but did you put the IP back in the exact same spot is was in? If not, the timing is now messed up.
And, speaking of timing, if the timing chain were to break, wouldn't that stop the IP from turning?

 

[Tanabi]

probably not related, but did you put the IP back in the exact same spot is was in? If not, the timing is now messed up.
And, speaking of timing, if the timing chain were to break, wouldn't that stop the IP from turning?

Yeah, I put the peg in the same place it was in when I removed it, and lined up the notch on the engine to the notch on the IP. Maybe I'm crazy but it doesn't look like there's really a way to put it in wrong, because of that peg... it won't mate if its in wrong? But anyway, I'm certain I put it in where it's supposed to go, and the fuel return line should still gush even if the timing is wrong.

And you're right, if the timing chain broke it wouldn't spin. However, when I put my fingertip to the IP intake to see if there's suction, I could feel a very slight pull, so it seems like it's trying to suck. I guess it may be my wishful thinking, cause if it is sucking, where is it sucking to?

 

[Milcommoguy]

I read a lot of fuel this and fuel that. (very important) Is there fuel in the IP housing? Couple of screws or pull the vent line and crank. Any fuel at one of the injectors ?

Did you check the electrical side of the equation? My previous reply above. If rebuilt, did they know it was a 24 volt system ? And lastly two words "glow plugs"

Lots of If's...

Two more words, GOOD LUCK, Hang in there. oops, that's three.

CAM, Waiting for Varoom VAROOM!!

 

[Tanabi]

I read a lot of fuel this and fuel that. (very important) Is there fuel in the IP housing? Couple of screws or pull the vent line and crank. Any fuel at one of the injectors ?

Did you check the electrical side of the equation? My previous reply above. If rebuilt, did they know it was a 24 volt system ? And lastly two words "glow plugs"

Lots of If's...

Two more words, GOOD LUCK, Hang in there. oops, that's three.

CAM, Waiting for Varoom VAROOM!!

I had already tested the electrical and heard the 'click' from the solenoid before I posted this, actually. Also tested voltage level, etc. One of the first things I tested. I didn't tell the rebuilders that it was a 24 volt system, so that could be my problem there. Next time I am able to get them on the phone, I will ask about that.

No fuel is coming out at the injectors. I actually have all my injector lines unplugged and stuck in mason jars so I can see what's going on easily and not make a mess. No fuel is passing from the input to any of the outputs on the IP.

I guess I can open the top of the IP housing and see what's going on up there, check the solenoid and such. That's probably my next step here, that and checking in with the rebuilders about the 24 volt system.

 

[KRedd]

https://www.steelsoldiers.com/showthread.php?171563-HMMWV-A1-Introduction. This explains the HMMWVs systems. This is on steel soldiers.