M1009 - Fuel delivery problem?

[Gunfreak25]

Mine ran fine for a year on a shot lift pump. When I changed filters and it wouldnt prime is when I found it was toast. I put a 10 psi electric on it on the frame, with no change in performance. Mind you this truck is in tip top shape, no air leaks, low miles etc.

So I can't speak for all trucks, some run more advanced or retarded timing wise, varying conditions of individual injection pumps, fuel delivery settings, etc.

I know GM had a few diesels in the 80s like the LUV that didnt even come with fuel pumps of any kind.


Sent from my SM-G955U using Tapatalk

 

[Matt5]

Don't hold me to the pictures...

But look at how the float sits and the sock...

Also a 305 has more power than a 6.2.

Knowing that you still have the break up issue and are not at your listed location but near sea level, I would check fuel pressure before pulling the IP unless you just want a rebuilt ip and want the job of replacing it...

My truck with a bad fuel pump lost power and from a stop I can 100% feel the power difference between my great dead car quest pump and the used one on it now. YMMV.

 

[Merddin]

I read on the stupid internet that the compression was higher. Who knows? The j code apparently had different heads than the c code. If the motor puts out around 165 hp like I stated before, or 155 hp, it is still 25 -35 more hp than a c code. Now whether the increase was due to more fuel at IP, higher compression, bigger valves, or lack of emissions control, I don't know. I researched this for hours months ago and that was what I found.

Many vehicles have been detuned or improved by changing heads or pistons. If the c code and j code has different heads, then either the amount of air flow or the compression is different. The lack of emissions would help some but not 20-30 hp. So then , the power increase is from more fuel, more air, more compression or a combination of the three.

Now everyone can nitpick my reasoning. Have at it.

 

[Merddin]

http://www.dieselhub.com/idi/6.2-gm.html

See compression and hp sections in middle of article. The j code code motor had the code of LL4. Interestingly, it seems the compression was raised during production years but still lower than the c code. I learn something everyday! My m1008 is a 86, so I assume the hp is 165 at the motor.

 

[cucvrus]

Reading directly from the military TM 9-2320-289-10
Across the board M1008/M1008A1, M1009, M1010, M1028/M1028A1/M1028A2, M1031. All listed in the TM as 135 BHP at 3600 RPM. So not sure where the other ratings came from. I read it on the emissions sticker also. Not to argue. I just don't want to cloud my mind or others with incorrect data. Been a long time and certain things I know and remember. That covers all models built from 1984-1987 during the CUCV build. Roll on. Have a Great Day. What's a few HP when you have 135? And I did have CUCV's that ran as good or better then a 305. My Mule M1009 was one of them. It ran great and was very efficient. Never checked the mileage so can't quote MPG. I never drove a truck/CUCV for efficiency or power. I think I would have been disappointed if that was my goal.

 

[Merddin]

I have a k5 with a 305 in it and it is a turd. The cucv has more torque for sure.

Back to original question of thread did the owner ever figure out the problem? If fuel filter was changed, then most likely IP needs work like cucvrus mentioned initially. What about air cleaner? Is it fresh?

 

[79Vette]

So its been a long time since I updated this thread. A couple weeks back I cut the end off the sending unit and brazed on an extension, lowering the pickup several inches and deleting the filter "sock" on the end. I also bent the float rod so it sits level with my extended pickup inlet at the bottom of its travel, and still swings all the way to the top of the tank. When I initially pulled the tank the gauge read "E" with 10 gallons left inside; when I put those ten gallons back after the modifications it now reads ~1/4 full.

I got the fuel tank reinstalled with all new rubber lines (except the really big hose to the filler neck), and extended the pickup on the sending unit to reach closer to the bottom of the tank. So to date, I have replaced the lift pump and the firewall fuel filter, all the rubber lines from the tank, and deleted the filter "sock". The truck is still a tad slow, but I knew it wasnt a racecar when I bought it. It now will run at highway speed without misfiring/shuddering terribly and makes at least as much power as my 305 powered Blazer did. I dont know which of the repairs had the most effect, but I am satisfied with how it runs. I drove from LA to Barstow and back last week to pick up a Dewey 24V DC generator (aka "BAPU") from that auction website, and the truck ran well for a 35 year old MV and averaged around 17 MPG. Overall this is a big improvement over 14-15 mpg and being borderline-undriveable on the highway.

I picked up a CUCV injector pump core from an outfit in Pennsylvania (Hillbilly Wizard) for $150 which I am going to get rebuild at Diesel Care based on recommendations from this thread. Plan is to eventually swap in that rebuilt pump and keep my tired (but known to work) pump on hand as a spare.

Here are some pics of the sender modifications I ended up doing. Notice how much straighter (thus longer, and with greater travel) the float rod is in the last pictures than in the first one. This gives an idea of how much fuel capacity was added by lengthening the pickup:

Original pickup geometry


Extension mock up:


Tube brazed on:


Modified float at "Full"


Modified float at "Empty"

 

[Keith_J]

The sock is needed when the tank is less than 1/4 full as it prevents drawing air into the lines. And keeps slime out. Socks can be easily cleaned with Diesel Mechanic in a Bottle. Berryman B12 carb cleaner also works.

As far as the problem with this vehicle, it sounds like one of the plungers is stuck. There are two plungers in the pump (hence the 2 in the title of the pump) and the only forces causing them to take fuel is charge pressure and centripetal acceleration of the rotor (half crank speed). The plunger is a little over 1/4" in diameter and about 1/2" long. It fits in the rotor with a clearance measured in millionths of an inch so any microscopic debris/corrosion can stick it. With only one plunger, half the fuel is injected.

Good call on a working core, rotor issues are usually not repairable and most shops won't give core credit.