M1009 - Fuel delivery problem?

[79Vette]

Hey folks,

I've been reading on this forum for a few years, and finally got my new-to-me M1009 a couple months back. Bought it just north of SLC Utah after wrecking my 82 K5 offroading, and road tripped it back to Los Angeles the next day. It did just fine for an old truck that had been neglected for awhile, but seems to have a fuel problem of some kind.

I was only getting 15mpg or so and it struggled big time on the hills. Running 65-70 on the flat is no problem, but even with the truck empty it couldn't maintain speeds over 45mph on any sustained uphill climb. Also at anything past 3/4 throttle the engine will start to miss while going up a hill, and anything over 1/2 throttle doesn't really make a difference in power. I realize the 6.2 and 3.08 gears are not a performance combo, but I would expect that the truck would be able to go up a hill empty without an issue...

I have since replaced the leaking lift pump and the fuel filter, and now there are no more leaks. But any throttle over 1/2 still does not make a difference in power, and I still cannot climb hills at speed. I am thinking the fuel tank sock might be plugged up, or the injector pump might be on the way out. I am familiar with GM square bodies but new to diesels, and would appreciate any advice to help narrow down what to repair next. The pump is big bucks to replace, and pulling the tank is a lot of work. I'm hoping there is something else simple I can try, but not sure what it would be.

Pic of my K5 family, left to right:

• 77 Jimmy; 350/TH400/NP203
• 86 M1009; 6.2/TH400/NP208
• 82 Blazer, now a parts truck 350/700r4/NP208. Air lockers in both axles, winch, lights, roof rack, HAM radio, and all the other off road toys

 

[cucvrus]

If you don't like hard work you bought the wrong 30 year old vehicle. May I recommend you drop the rear tank and skid plate and change the fuel sock and look inside the fuel tank real good. replace all the rubber hoses and then give it a try again. If it still runs poorly the next thing is a rebuilt injection pump. Regardless of where you go someone will have had a bad experience with that rebuilder. I have replaced no fewer the 50 of the injection pumps and the little Mom and Pop shop that rebuilt them for me for many years has closed and retired. I have been using Diesel Care in Memphis. I have had no problems with the injection pumps I get from them and they are about $350. I never wrote down any numbers from my pump. I just got a pump out of my stash and they sent me a pick up tag. I boxed the core pump up attached the tag and about a week later a clean rebuilt pump came is 3 hours I had a perfect running CUCV. It always worked for me. Good Luck. But expect to have work on lots of things until you get it dialed in. I run stock vehicles with no modifications electrical or fuel and have great results. I sold a few to members here and think they are still running them that way. My family had them for years but we have replaced them with more modern vehicles for more comfort. Have a Great Day.

 

[firefox]

This might help eliminate the tank and hoses as the problem: Get a long length of fuel hose and a clean fuel can. attach one end to the inlet to the filter and the other end in the fuel can. Make sure everything is secure, since you will probably need to locate the can inside the cab with the hose coming in through the window. Try to do this in a back area away from other cars. Please be careful!

 

[79Vette]

CUCVSRUS, I daily drive a 79 Corvette and have a 71 Honda motorcycle that I ride and wrench on for fun. This CUCV is 5 years newer than any other vehicle I have ever owned, and nearly a decade newer than the average of my old junk.

I appreciate the input, and I'm definitely not opposed to hard work or spending money where appropriate. I've just learned the hard way that it is often prudent to ask around for a second opinion before diving down a rabbit hole that might not be the right fix for my problem. At the point I am pulling the tank anyway, is it even worth putting the old one back in? They seem pretty cheap; is there any reason to not just replace it with new while it is out? I think I would prefer a 31 gal anyway, all things being equal.
Agreed its definitely worth replacing the rubber lines once everything is unhooked anyway.

Firefox, good idea on confirming the tank/lines/sock are the problem and not something else. I would have to get the truck up to speed though, as the problems only show up under load. It will start and idle fine as-is but will not make power when loaded. If I can figure a safe way to secure a fuel can in the cab I might give it a try, or maybe just drop the tank. Not sure which would be easier honestly.

 

[johnjr]

Try an outboard boat gas can.

 

[cucvrus]

Try an outboard boat gas can.

Of course making sure it has no gas in it. Or maybe so if it has 2 cycle oil in it. LOL
Honestly I think you have a few issues playing into it. 1 the tank should be dropped and replaced sounds like a good idea. The fuel pick up sock can be replaced or eliminated. I have heard people say no need for the sock when you service the filter regularly. I see that point also. 2 The rubber hoses replaced. 3 fuel filter replaced with new cartridge. 4 last but not least the injection pump rebuilt. These vehicles sat around a lot over the past 30 years and they have not been treated nice by people. Many feel into bad hands after the military and have been hacked and beat severely. So assuming you have a clean decent vehicle. I am giving you my experience and advise. No more. That is all sight unseen. Good Luck.

 

[79Vette]

So I finally got a weekend away from work, and pulled the tank this morning. I ran the truck until the fuel gauge was just above the "E" line and I figured the tank would be about empty, but it was heavier than I was expecting it to be. Once I got it out on the ground, I emptied the tank out with a transfer pump and filled up 2 entire 5 gallon cans with diesel. Measuring the tank, it is over 12" deep from the flange where the sender goes to the bottom. The very bottom of the sender float is 10" from the top flange on the sender, so when it bottoms out there is still over 2" from the end of the sender travel to the bottom of my tank. I think the 31 gallon tank is supposed to be ~13" deep, and the 25 gallon is ~11". Do I have a 31 gallon tank with a 25 gallon sender?

Also looking around inside, it looks pretty clean already. Definitely not what I was expecting to find. I think I am going to take the "sock" filter off and just put everything back with new rubber lines.

Unfortunately, I still have no idea why the truck suffers so badly on hills. With the tank this clean and a new lift pump and filter, the only thing I can think of is the injector pump and injectors. Any advice?

 

[cucvrus]

I would go with a rebuilt injection pump. I have never had to replace a nozzle to date for power or performance issues. I have replaced a few for external leaks. I have taken them to a shop and had them checked also. Every time they say they are fine. I had a 7.3 NA Ford diesel. It was running poorly I was told the nozzles were bad I changed them it ran the same. I changed the injection pump it was like a new truck again. If it were me I would have the injection pump rebuilt. it seems to cure a lot of issues all at once. Makes the entire engine run better and more efficient. Starts easier, idles smoother and runs stronger. Good Luck. I am assuming the glow plug system and starting system function as designed. Have a Great Day. I was also told several time to ditch the sock in the fuel tank. It has a fuel filter that can be easily serviced. Unless you are dumping dirt in your tank.

 

[Matt5]

I have, 5 of these things out here, they all pretty much do nothing past 1/2 throttle...

What is your elevation I am seeing near 5000 feet... you are already into thin air for the truck and then you are climbing hills to even thinner air?

You have some decent hills out in UT no?

You have a 5500lb shed with wheels, er I mean truck... with lets be real here... at sea level 30 years later... 120HP? (god only knows what you have a 5000 feet N/A... 100hp?) maybe? 3 gears in a tranny that is eating 25% of your HP (yes turbo 400 is good for like a 25% lose in power on it's own) with 3.08 gears...

Not sure what exactly you expect but... IMO.

Assuming my elevation info is correct (or close) I see nothing wrong.

Now the miss, did you correct that replacing the leaking fuel pump? I would get a pressure gauge in the fuel line, I just dealt with a huge disaster over a new (2 years) fuel pump not only dying (truck still runs with a dead FP just less power) but somehow BLOCKING fuel to the IP... if I had a pressure gauge... wow I would have saved so much grief...

What do you mean by "miss" is it knocking or is it really losing cylinders... Again a pressure gauge would tell you if you are getting 10psi to the IP or maybe pulling a vacuum, or was this issue fixed?

Any smoke?

You can send your injectors out to be tested or just replace them they are sort of a wear item good for 100k IIRC...

Since we dropping names, I used accurate diesel in MI for my IP... I thought my fuel pump issue was the IP long story short I called to see if I had warranty left (no) before opening the top of the IP (assumed incorrectly the solenoid burned out (it was a good assumption based off symptoms and history)) they offered one at a discount, and I ended up talking to the 6.2 guy for a good 30 min not only about the IP but other things chatting while getting some very good suggestions... I mean, that's impressive service to me.

Also fuel additive is a great plan IMO... our trucks needed the higher sulfur diesels... I myself run opti lube summer its cheap... its been shown to decrease wear, alot... and if you believe opti lube... they claim they still blow away everyone else in a recent test THEY did /salespitchnoaffiliation


TLDR, accurate diesel in MI for parts
5000 foot elevation? N/A motor? you should see a decent power lose
sea level 30 year old 6.2J maybe 125HP... bring it up to 5000 ft... about 15% power lose from that so... maybe 100hp?
3.08 turbo 400 (25% power lose from tranny)
5500lb truck...
Assume my numbers are right your motor is putting out about 100hp, your tranny is taking 25% your trying to go up hill with 75HP... in a 5500lb truck... with 3.08 gears.
She gona be slow even in tip top shape... put a turbo on if you want power and be amazed at the difference.

FYI I believe they have a high alt injection pump...


Just as a fun example, granted this is plowing but, plow on, weight in the rear... I would guess I was 9klb... I was climbing a good short hill (read, 15mph foot to floor?) I was *passed* (no passing area btw hill is maybe 3/4 a mile TOPS) like I was not moving (well I kinda was not LOL) by a 08ish 1500 that burned so much oil it never needed an oil change, with a plow and a sander on... oh and we both started from 0mph pretty much. So ya.

That is the power your 6.2 has... at 300ft elevation...

 

[rsh4364]

I installed a 31 gal tank in my 1009 and 31 gal sending unit, I ran it out of fuel. It took 30 gallons of fuel to fill to top. So maybe you have wrong sending unit...I would verify proper sending unit ,replace filter sock, replace fuel lines , install fuel pressure gauge, verify proper fuel pressure then replace the IP....My $s with cucvrus its probably the IP.

 

[rsh4364]

 

[Merddin]

J code 6.2 is actually around 165 hp and around 285 ft/lb of torque. Civilian model, C code, is 125-135 hp. J code has higher compression and no emissions junk.

Your problem sounds like a lack of fuel. Change fuel filter first. Cheap and relatively easy. Get a fuel additive. I am using stanadyne. Optilube sounded good but I can't get it locally and stanadyne made the injection pump. Take the truck on some long drives to get it up to temp and burn out all the built up gunk. If all that doesn't help it time for an injection pump.
Good luck!

 

[Hasdrubal]

J code has higher compression

Really? I am not aware of any compression ratio difference between the C-code and J-code. They should both be 21.5:1 Can someone in the know, chime in here..

 

[cucvrus]

New one to me. They are the same compression C & J. Never heard that a CUCV had 165. I was always in the 130 -135 HP range. Even with my stock fuel filter.

 

[cucvrus]

6.2L GM/Detroit Diesel Specs

Engine:	Detroit 6.2L V-8 diesel
Engine Weight:	650 lbs dry
Max Engine Speed:	3,600 rpm (4,000 rpm w/ no load)
Peak Horsepower:	Introduced at 130 hp @ 3,600 rpm, maximum offered during production was 143 hp @ 3,600 rpm. The United States Army's version was rated at 165 hp @ 3,600 rpm I think they are referring to the US Army version as the ones in the HMMWV. I could be wrong. I always read the emissions sticker.

 

[Gunfreak25]

I am also sending my IP in to Diesel Care in Memphis per the recommendations here. You can't beat $290 for a rebuild, even if they do just service all the seals and stuff, mine leaks like crazy after it sat for 3 years. Never a drop before that, driven daily.

My truck always kept 45 up hill unloaded if I pushed her. Which ain't terrible I guess for 3.08's. The only issues she had was too much washboard offroading (like badly grated dirt roads) and it would begin to loose power and eventually stall. If I let it sit for 10 minutes it would start right back up and run fine, only to peter out again. It would act like this even upon returning to town for a couple day's before returning to normal. My clear inline glass fuel filter at the time was found to be plugging up with rust particles so that's what I chalked it up to.

That was 3 years ago before I sold it. I have it back now and it leaks like crazy so i've rebuilt the whole fuel system and added a pre lift pump 10 micron and a post pump 2 micron filter, next is up is IP rebuild.

 

[Matt5]

Sea level is NOT 5000 feet...

Google to your hearts content you will find everything from 135hp to 185hp (stated hmmwv).

Attached is BANKS (graph) unknown if flywheel or rear wheel HP / motor code... note the curve...
Hard to read info graphic I can't credit as I forget, its a DYNO run (we can assume c code) and its sub 100HP... and we can assume it is altitude adjusted... so OP can cut 15% off those numbers... and add whatever the OP likes for "j code" (again assuming c code)
Also look at the effect temp made... running an air intake to the stock location on the rad support is not a bad idea at all...
Pretty sure my air cleaner sticker says 155hp... and that should be flywheel HP...

I am not saying the OP does not have a bad IP but you people really need to start factoring in the OP likely being around 5000 feet... anything over 4000 is "high elevation" for a 6.2...

Oh ya and compression was the same it was heads (valves / precups) and intake (egr) actually IIRC a few versions of these motors exist... forget what had what...

 

[79Vette]

I bough the truck in Salt Lake City, just over 4000 feet. Currently in Los Angeles, and not a real noticeable difference in drivability vs Utah. I am sure altitude makes a difference, but it cannot be as bad as what I am seeing (especially since the same problem exists at sea level, literally on the beach). I agree, its looking like the IP is likely bad and I will need to get it rebuilt.

At WOT it still starts breaking up around 2800 RPM (engine bucks/misses terribly to the point you need to let off the throttle, no smoke, no knock/preignition sounds that I can hear over the exhaust). So I am thinking something is wrong with it. No fuel leaks from the IP or elsewhere, now I replaced the lift pump, but it still seems like something is worn out. Starts right up in the morning, idles great, and will run fine at up to half throttle on flat ground.

Though back on the fuel tank/sender for a minute, does anyone know how to tell the difference between 25 and 31 gal senders? I have tried searching and they all look the same in pictures, and I am guessing the pickup and sender are ~2 inches longer on the 31 gallon variant. I would like to make sure I have the right sender for the 31 gal tank I seem to have, but dont know how to definitively do so without just buying a 31 gal one to compare. Once I get that sorted and reinstall the tank with all new rubber lines, I will be pulling the pump to send to Diesel Care per everyone's recommendation here.

Thanks again for all the help.

 

[Gunfreak25]

I cant help with the sender. But a side note on the lift pump, it has no effect on a properly running injection pump. Its main purpose is to help "lift" fuel to the IP and purge air out during filter changes. In fact many (myself included) will do a filter change only to find out the lift pump has been inoperable for some time, yet the truck runs just fine.



Sent from my SM-G955U using Tapatalk

 

[79Vette]

I do know the truck will run without a lift pump (or with a bad one), but I thought that could cause fuel starvation? IE if the injector pump has to pull vacuum on the filter and lines from the tank, it can starve for fuel at higher RPM. Supplying a few PSI from the lift pump pushes fuel through the filter and helps prevent fuel starvation. Is that not the case?