m35a2 losing prime

[benand117]

i think my m35a2 is losing fues prime. if t sitfor even 5 mnutes on level ground or parked up hill it cranks for 30-45 seconds before it will start. but not so much if parked down hill. i don't like cranking it that long without oil pressure and it's hard on the starter. it even does it when it's warm. but when it's started it runs great, so i don't think it's the lift pump or the injection pump. is there a inline check valve or something that could be causing the fuel to drain pack into the tank. any help wold be great.

 

[DUG]

Check the primary fuel filter. Mine used to come loose until I switched to Westfolk's spin ons. On my 2008 GMC Duramax I had the same problem - I didn't get the filter tight when I changed it and several months later it started losing prime.

 

[Heavysteven]

I would do the following.

1. Check/replace fuse for in tank fuel pump
2. Replace fuel filters/gaskets
3. Confirm tank pump runs and bleed the fuel system of air from secondary and finail filter housing.

 

[benand117]

m35a2 losing prine

i think my m35a2 is losing fuel prime. if it sits for even 5 mnutes on level ground or parked up hill it cranks for 30-45 seconds before it will start. but not so much if parked down hill. i don't like cranking it that long without oil pressure and it's hard on the starter. it even does it when it's warm. but when it's started it runs great, so i don't think it's the lift pump or the injection pump. is there a inline check valve or something that could be causing the fuel to drain back into the tank. any help wold be great.

 

[Clay James]

Can you hear the in tank pump running?

 

[wsucougarx]

Hmm, sounds like you may have air in the fuel line. Have you gotten under your truck and inspected ALL your fuel lines for leaks?

 

[Djfreema]

Another area to check is the fuel return lines between the injectors. Go through and tighten all the fittings including the flame heater fittings. If the lines are a little loose then it allows air to suck back in as gravity pulls the fuel back to the tank when the engine is off. It fixed my long cranking starts on one of my past trucks.

 

[rosco]

My bet is the lift pump. Crack the bleeder on the secondary filters with the engine off, accessory switch on. If fuel doesn't come gushing out, its the problem. Also loose fittings else where would tend to leak when the lift pump is running. Just because its running, doesn't mean that its working/pumping.

 

[roger-wilco-66]

When your tank pump is running, and you open the vent (bleed) on the primary filter, do you get fuel?
If this is the case, and taking it one step further, when you open each secondary filter bleed valve, is there something coming out with a reasonable pressure?

Cheers,
Mark

 

[clinto]

benand117, I merged your two identical threads. Please do not cross post identical topics/threads in multiple forums.

Additionally, this topic really isn't appropriate for the "deuce modification & hot rodding" forum-that forum is for topics related to modifying deuces-you are trying to repair one back to stock specs. Therefore the deuce forum is the appropriate destination for you.

Thanks

C

 

[benand117]

yeah yesterday was my first day on the site. i posted it in the modification section not knowing about the one about stock trucks. i didn't know how to delete the other post. i'll get better at it. thanks about all your help guys. i have all the fuel filters i'm going to do all those checks today after work. might as well change the filters while i'm down there. i'll let you guys know how it goes.

 

[rosco]

Fuel should gush out of the bleeder! You will know that the bleeder screw should naturally be closed. I have only one bleeder on the secondary filters, so it does both at once. Same for the primary.

 

[rlwm211]

If your lift pump is working, you cannot "Loose your prime" . If you turn the power on you should fill all the filters and lines in 10 seconds maybe a bit more. If in fact you are "losing your prime" leaving the power on and not cranking is the proper way to re-prime the system.

Other posts have suggested you check to see if the lift pump is working at all. I strongly suggest you follow that advice as you will eventually burn up your starter if you are always starting your truck without the lift pump.

RL