Engine pulsing while running

[pinwormfood]

Hi guys, I looked around in the forum and couldn't find a thread on this although I am sure there is one somewhere. Hopefully you guys can help.
I park my truck on an incline at night, sloping down to the rear of the truck. when starting the truck this morning, it started, and then run for a few seconds and died out. i turned it over again and after a few seconds of cracking, it started up, run for a few seconds, and then died out again. it has the syptoms of running out of gas, but i have a 1/4 tank. could the diesel be flowing back to the tank while sitting? if that is true, and it is losing pressure, then there must be an air leak in the fuel line right?

ok, so after cranking it over a few more times, it started running, and kept running. now while running, the engine pulses like a mofo. up and down, up and down.
any ideas?

thanks guys, much appreciated.

oh, and i am in need of an oem flex plate (flywheel). nos if someone has one. i don't want to put a used fatigued one on after pulling the trans. thanks

 

[tshermankb]

I had the exact same problem. it was all my fuel filter housing. both the ICE sensor and the water drain plug were leaking hard. plumbers tape and a freeze plug got her airtight. the 6.2 starts and runs great now well below freezing plus it upped my mileage from sub 15mpg to the mid 20s (25 on my last trip !)

 

[dependable]

You probably have an air leak in the fuel filter housing. this is a common problem with many posts about it. If oem surplus still has the improved fuel filter base for sale, that is your best bet, costs about $60 plus shipping.

 

[Braunchitis]

I was having this problem a few weeks ago, a new fuel filter fixed it.

 

[tshermankb]

hahaha 3x the same answer. seriously though at least try the freeze plug fix first it is insanely easy and costs a 25cents. unless your housing is cracked there is no need to get a new one.

well actually unless you want to build the engine and need more fuel flow. in witch case you really want a better fuel filter like the Racor 90gph unit (RPH90?)

PS. I can repost photos if it helps

 

[ODdave]

AIR. the CUCV fuel systems WORST enemy

 

[Wolf.Dose]

OK, the fuel filter base problems are mentioned allready. Die cast junkt made for ten years or so. Fuel filter seals are not made for ever. So change for a modern truck fuel filer system, for example Mann & Hummel and forget these problems.
Hovever, ther is an other one. If the little fuel pumps at the injection pumps is not ok, means the little pump blades are worn out, the system is leaking and selt draining, for the injection pump unfortunately is the highest part of the system. And if you shutt off valve in the pump is in addition not closing propperly (however good enough for shutting of the engine), the fuel will run back and drain the injection pump to a certain contaent to make starting difficult. I had that problem in 1991, when I bought my M1009. The solution was a new injection pump.
Wolf

 

[pinwormfood]

just checking if this is the one. it says it's for crew cab, not m1009, not sure if they are the same....it was the only one i found on there.
http://oem-surplus.com/gmwp/picpages/filterassy1725.html
part number 12471725
any help would be great.....
thanks, pinwormfood

 

[pinwormfood]

i would love some pictures if you could....that would rock. thanks pinwormfood.
pictures help me to identify things. i really don't have anyone that knows about autos that i can ask for help. it's very much appreciated.
pinwormfood

 

[pinwormfood]

can anyone tell me where they would start to find the air leak....is there a start to finish procedure for testing for them?
perhaps a link?

 

[Warthog]

can anyone tell me where they would start to find the air leak....is there a start to finish procedure for testing for them?
perhaps a link?

The troubleshooting section of the TM 9-2320-289-20 specifically talks about the pulsating at idle and has a step by step procedure. You can download it from the Resouces tab at the top or by going to the CUCV Forum and opening the "CUCV FAQ Article" at the top. This Wiki page has alot of info and has all the Tech Manuals already linked.

Also the "FAQ Thread for CUCV's" has alot of additional info but has become cluttered with useless posts

oh, and i am in need of an oem flex plate (flywheel). nos if someone has one. i don't want to put a used fatigued one on after pulling the trans. thanks

NAPA has them, you will want to make sure you get one for the 6.2 diesel, engine code J and the TH400 tranny. I have also seen them on Ebay. GM also has them. GM Part number 14077157

 

[pinwormfood]

i looked in the troubleshooting of that manual, and didn't see anything about pulsing.....
perhaps it was another manual. i appreciate any other help and advice you might have. thanks, pinwormfood.

 

[Wolf.Dose]

Flywheels/flex plates are no problem look for one with 6 torque converter bolt holes.
Trubble shooting starts at the fuel pump, means check feeding pressure. Than the fuel filter assy for leaky spots and/or damaged seals. This part can be replaced by a modern truck cartridge fuel filter assy, for they usually include a water seperator at the botom of the filter cartridge. Must be installed vertical. The electric connections on the original filter assy are not realy needed.
After that you have to check the lines for propper tightnes and not dripping, those routing to the injection pump. If this is all ok, the retaining valve at the little load pump on the injection pump probably is not ok any more. That means a new injection pump, if you can not canibalise an other pump with propper parts and do this by yourself. Shops usualy will not do this, they like to sell a rebuilt or new part due to production liability laws.
Hope this helps.
Wolf

 

[stampy]

Spin on filter solved my problems!

 

[tshermankb]

generally anywhere that is leaking air is going to also leak fuel so look for places saturated with diesel heres some photos of my air leak fix