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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1668
Experience:  GM Grand Master Technician 2007. 14 year experience.
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I have the occasional "fishbite". Usually get a quick puff

Customer Question

I have the occasional "fishbite". Usually get a quick puff of black smoke then goes away. Just replaced fuel sender and sock, cleaned the tank. Replaced lift pump, FFM screen and filter. No codes. Any suggestions?
Submitted: 1 year ago.
Category: GMC
Expert:  Gm Tech (Cam) replied 1 year ago.

HI there, I am Cam. Does this seem to be worse when it gets warm?

Is there anything thing you can think of that makes it worse or better?

Customer: replied 1 year ago.
It seems to happen lately when I'm parking, at an idle then little throttle and idle again. Possibly right when I step on it or take my foot off the pedal. Can't say it's ever done it when the engine is cold. Im getting a steady 4.5-5.5 psi fuel pressure to the FFM at an idle.
Expert:  Gm Tech (Cam) replied 1 year ago.

Did you relocate the Pump Mounted Driver from the side of the pump?
Any wiring issues there?
More hot than cold?

Customer: replied 1 year ago.
My PMD is in the grille with a long harness, I cooked the old one and it's still on the IP. I've never had any sort of trouble like this before. Just replaced the waste gate solenoid, that fixed my turbo surge. Installed 3" down pipe and 4" from there. Going to replace the IAT sensor and mapsensor tomorrow. Runs great other than the odd fish bite.
Expert:  Gm Tech (Cam) replied 1 year ago.

Does wiggling the wiring change anything?

Customer: replied 1 year ago.
I never tried. I could try a different harness. I was thinking of getting a spare PMD just in case.
Expert:  Gm Tech (Cam) replied 1 year ago.

Not a bad idea. Considering how vital the PMD is, and how often they fail, it’s a good idea.

Customer: replied 1 year ago.
I'm worried my IP might be on its way out. Has a worn one been know to cause this?
Expert:  Gm Tech (Cam) replied 1 year ago.

This is not a common complaint, normally the pump failure is a stalling or no start issue.

Customer: replied 1 year ago.
I read online that a leaky donut on the crossover might cause this or air in the fuel.
Expert:  Gm Tech (Cam) replied 1 year ago.

The leaking exhaust you would hear though.
Air in the fuel, Usually don't get that with a lift pump and if you are getting that pressure, its not as likely. I have heard though of lift pump failures sending debris through the system. Is there garbage in the fuel filter?

Customer: replied 1 year ago.
I just replaced everything right up to the filter in the manager. It did this before with the old filter, dirty sock, fuel tank and sender.
Expert:  Gm Tech (Cam) replied 1 year ago.

Ok, lets see what the new harness will do.

Customer: replied 1 year ago.
Yeah I'm out of options.Is it going to hurt anything while I try and figure this out?
Expert:  Gm Tech (Cam) replied 1 year ago.

No, it should not.

Customer: replied 1 year ago.
OK. Sounds good. I'll try the harness
Expert:  Gm Tech (Cam) replied 1 year ago.

Ok, reply at that time.

Customer: replied 1 year ago.
Will do, thanks
Expert:  Gm Tech (Cam) replied 1 year ago.

ok ( If you reply, I cannot proceed with other customers until I answer you). Talk to you tomorrow.

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