Mechanical Fuel Pump not working? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

rough69 · 05-22-2007, 07:43 PM

Well this has me stumped now officially.

On my '69 C10 350, I can't get the fuel pump to push / creats psi. it seems.

I even removed the fuel sending unit sock, blew through the fuel line, and everything seems ok there. Added like 3 gallons to the tank and checked that the sending unit is dipped in.

I even tried hooking a fuel can directly to the fuel pump and it still would not run.

The only time I can get the engine to fire for a short time is when I dump gas down the throat of the carb.

Timing is set properly as the truck does sound healthy when it fires for the few seconds it can. The carb was removed from a runner.

Everytime I look at the clear filter (Fram G3) it is dry when I am cranking. I tried cranking with the fuel line off the carb, it doesn't "squirt".

I even tried replacing the fuel pump with another sapare one I had lying around but same thing.

What are the odds that both pumps are bad? Is there a way to check the diaphragm?

Is there a possibility that the fule pump rod thing is screwed up (it is there). How can I check that?

Is it possible the lobe on the camshaft is nuked?

I'm damn close to just slapping an electric on it but I hate having a damn eggbeater / blender / rock tumbler under my truck.

**phase_one** · 05-22-2007, 08:29 PM

That happened to me I did all you did until I bought a fuel pump that worked and then the pick up fired up and ran.

JimKshortstep4x4 · 05-22-2007, 08:30 PM

The last time that I had a similar problem with the fuel pump, it turned out to be the push rod was not staying on the cam. (The cam would push it down but the pump spring would not push the rod back. In my case it turned out to be the rod was being held by a bolt that went too far in the front of the engine. (There are a couple of holes in the lower front part of the engine that are threaded 3/8"-16). If there are bolts in these holes back them off to check if you have this situation.

Jim

**kwmech** · 05-22-2007, 08:37 PM

Have you checked all the rubber lines to make sure it is not sucking air?

Longhorn Man · 05-22-2007, 08:37 PM

that bolt hole is there intentionally to hold the pushrod up when you are swapping pumps. You remove the short bolt, install a longer one, then re-install the short one again after the R&R on the pump.
Just FYI.

rough69 · 05-22-2007, 11:28 PM

JimK that was a great idea and I did not know that was there for that purpose.

I loosened up the small bolt that was in the top hole (no bolt in the bottom) and it didn't make any difference.

Also, when I swapped pumps the rod didn't bind or anything, it slid all the way down and I used a magnet to prop it up and pumps.

I honestly think I have 2 bad stock pumps maybe?

Or, how possible is it that the pump rod / cam lobe is damaged?

I'm going to order a new Holley Mech. Pump I think...

Quote:

Originally Posted by kwmech

Have you checked all the rubber lines to make sure it is not sucking air?

All of them look decent... /shrug

JimKshortstep4x4 · 05-23-2007, 05:31 AM

It is possible to have two bad pumps. Did you try working the arm on the pumps by hand to see if they would pump?

It is possible for the lob to be worn but I have not seen it happen.

Jim

rough69 · 05-23-2007, 10:42 PM

I did try working them by hand but they were damn hard to and I only got a puff out of the inlet, no psi on the outlet.

So I sacked up and bought a Holley #12-834 and it runs great!

Guess I did have 2 bad pumps, what're the odds...

05-22-2007, 08:29 PM	#2
phase_one Registered User Join Date: Jul 2001 Location: Praireville. LA 70769 Posts: 390	Re: Mechanical Fuel Pump not working? That happened to me I did all you did until I bought a fuel pump that worked and then the pick up fired up and ran. __________________ 11 Surbaban 70 C 10 still in progress

05-22-2007, 08:30 PM	#3
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Mechanical Fuel Pump not working? The last time that I had a similar problem with the fuel pump, it turned out to be the push rod was not staying on the cam. (The cam would push it down but the pump spring would not push the rod back. In my case it turned out to be the rod was being held by a bolt that went too far in the front of the engine. (There are a couple of holes in the lower front part of the engine that are threaded 3/8"-16). If there are bolts in these holes back them off to check if you have this situation. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

05-22-2007, 08:37 PM	#4
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,391	Re: Mechanical Fuel Pump not working? Have you checked all the rubber lines to make sure it is not sucking air?

05-22-2007, 08:37 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Mechanical Fuel Pump not working? that bolt hole is there intentionally to hold the pushrod up when you are swapping pumps. You remove the short bolt, install a longer one, then re-install the short one again after the R&R on the pump. Just FYI.

05-23-2007, 05:31 AM	#7
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Mechanical Fuel Pump not working? It is possible to have two bad pumps. Did you try working the arm on the pumps by hand to see if they would pump? It is possible for the lob to be worn but I have not seen it happen. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

05-22-2007, 07:43 PM	#1
rough69 Registered User Join Date: Apr 2007 Location: CA Posts: 60	Mechanical Fuel Pump not working? Well this has me stumped now officially. On my '69 C10 350, I can't get the fuel pump to push / creats psi. it seems. I even removed the fuel sending unit sock, blew through the fuel line, and everything seems ok there. Added like 3 gallons to the tank and checked that the sending unit is dipped in. I even tried hooking a fuel can directly to the fuel pump and it still would not run. The only time I can get the engine to fire for a short time is when I dump gas down the throat of the carb. Timing is set properly as the truck does sound healthy when it fires for the few seconds it can. The carb was removed from a runner. Everytime I look at the clear filter (Fram G3) it is dry when I am cranking. I tried cranking with the fuel line off the carb, it doesn't "squirt". I even tried replacing the fuel pump with another sapare one I had lying around but same thing. What are the odds that both pumps are bad? Is there a way to check the diaphragm? Is there a possibility that the fule pump rod thing is screwed up (it is there). How can I check that? Is it possible the lobe on the camshaft is nuked? I'm damn close to just slapping an electric on it but I hate having a damn eggbeater / blender / rock tumbler under my truck. Last edited by rough69; 05-22-2007 at 07:44 PM.

05-23-2007, 10:42 PM	#8
rough69 Registered User Join Date: Apr 2007 Location: CA Posts: 60	Re: Mechanical Fuel Pump not working? I did try working them by hand but they were damn hard to and I only got a puff out of the inlet, no psi on the outlet. So I sacked up and bought a Holley #12-834 and it runs great! Guess I did have 2 bad pumps, what're the odds...



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