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Yesterday I was driving my 77 and all of a sudden it started missing badly whenever I reached third gear or accelerated hard. When I got home I noticed that the return hose on the fuel pump was disconnected and fuel was pumping onto the ground. I replaced fuel return line hose and thought everything would be good to go. It is still doing the same thing. Takes off great in first gear and runs fine in second but as soon as I get into 3rd gear it falls on its face. Engine cuts out completely then refires over and over. If I slow down and give it just partial throttle it is ok. It feels like a fuel starvation issue but could it be ignition related? Fuel pump?
By the way, I replaced the fuel filter at the Q-jet, no help.
Sounds like you got it right. I just had my second pump fail and same symptoms both times. It falls on it's face a the top of second gear when accelerating hard. both pumps did this rather than just flat out stop pumping fuel.
For a SWAG, might the return hose be clogged in which case there would be back pressure reducing fuel flow. The fact that you found it blown off might indicate a clogged line.
Normal psi on the pump should be about 6 or less for a q-jet. My new pump is rated at 6 psi as well. I usually regulate it down to 4 psi. It runs good there. Where it started having problems was when dropping below about 2 psi. Even showed 1 psi but still ran fine except full throttle.
Are you using a preformed S shape return hose? Regular fuel hose could kink and potentially blow off. Never seen it happen, but possible.
I just installed a new Carter 3 port fuel pump. Caused me issues, I put a gauge on it, it showed 9 psi. Way too much for QJet. I'm running a regulator for now down to 5 psi, until I can get a pump that puts out pressure within specs. Very frustrating.
Are you using a preformed S shape return hose? Regular fuel hose could kink and potentially blow off. Never seen it happen, but possible.
I just installed a new Carter 3 port fuel pump. Caused me issues, I put a gauge on it, it showed 9 psi. Way too much for QJet. I'm running a regulator for now down to 5 psi, until I can get a pump that puts out pressure within specs. Very frustrating.
The carter M6955? That's the one I just put into mine in the last month. Mine was producing a little over 6 psi. I have a regulator and a gauge so no issue, just regulating it down. The new pump seemed pretty sloppy in manufacturing so I wouldn't be surprised if one did put out less or more than 6 psi.
The new pumps also have a longer lower section which places the ports lower.
Not a problem for the return but could be for the preformed "S" line potentially, not really sure as I'm not using one. I have an S line I made myself so I could adjust the length to what I needed.
Thanks for all the suggestions everyone. I received my fuel pump today from Corvette Central. I also ordered a metal fuel line replacement between the pump and carb. We will see.
For a SWAG, might the return hose be clogged in which case there would be back pressure reducing fuel flow. The fact that you found it blown off might indicate a clogged line.
I was thinking that too, but when I reconnected everything there appeared to be plenty of fuel returning to the gas tank when I looked down through the filler hole.
The carter M6955? That's the one I just put into mine in the last month. Mine was producing a little over 6 psi. I have a regulator and a gauge so no issue, just regulating it down. The new pump seemed pretty sloppy in manufacturing so I wouldn't be surprised if one did put out less or more than 6 psi.
The new pumps also have a longer lower section which places the ports lower.
Not a problem for the return but could be for the preformed "S" line potentially, not really sure as I'm not using one. I have an S line I made myself so I could adjust the length to what I needed.
Originally Posted by Heus
Thanks for all the suggestions everyone. I received my fuel pump today from Corvette Central. I also ordered a metal fuel line replacement between the pump and carb. We will see.
REELAV8R is correct about the issue with M6995 pump being too long at least for 77-81 vettes. Everyone lists this as correct for 70 to 81, but it is not. I recently changed my pump and initially ordered an Airtex 41240 which is listed as being for a 77-81. But what you get is an Carter M6995 pump in an Airtex box. Apparently one company bought both Carter and Airtex and decided to only make one of the fuel pump styles. The one with the longer bowl will bolt up to the engine OK, but will not align to the proper fuel line for the 77-81 vettes. Note that vette central lists one pump for 70-81, but different fuel lines for the 70-76 vs. the 77-81's. I returned the Airtex alias Carter pump to Rock Auto and then bought a Delphi MF0026 from Autozone. The dimensions match the original pump on my 80 and it aligned well with the fuel line with just minimal bending by hand.
Here's the thread on my job replacing the pump. A lot of members provided good advice for the job.
Here's the pump that Corvette Central sent me. Yes it is deeper than stock. I guess the new fuel line that I also bought that goes from carb to pump won't work. You would think Corvette Central would know better. Return nipple seems to be bent upward as well.
And unlike the one in the photo at CC, I bet it doesn't say Made in the USA anywhere. CC customer service is very good. If you call them, tell them that it doesn't fit and is not made in the USA per their photo, they'll take it back and refund including all shipping.
And unlike the one in the photo at CC, I bet it doesn't say Made in the USA anywhere. CC customer service is very good. If you call them, tell them that it doesn't fit and is not made in the USA per their photo, they'll take it back and refund including all shipping.
and I already notified them…no change…
that pump should still work…a correct pump is unobtainium….anywhere..regardless of country
Last edited by interpon; Sep 11, 2021 at 07:54 AM.
and I already notified them…no change…
that pump should still work…a correct pump is unobtainium….anywhere..regardless of country
Interpone, yes it work, but not with the correct 77-81 fuel line at least note without reshaping it, but I don't know if it can be bent enough to reach and not end up interfering somewhere else. It's a tight fig along the block
But why go through the hassle. Send it back and get the Delphi MF0026 from Autozone or wherever. It is the correct fit for 77-81's.
Guess I should have gone to Carlisle this year and gone to every vendor to debate this with them. It might have been worth the price of admission.
In any case, I did submit a review of this at CC. It'll be interesting to see if they post it.
Last edited by vince vette 2; Sep 11, 2021 at 09:29 AM.
Here to report that my metal fuel line fit the Carter pump and Q jet. Haven't driven the car yet to see if this fixed my problem watching my Buckeyes against Oregon now.
Here to report that my metal fuel line fit the Carter pump and Q jet. Haven't driven the car yet to see if this fixed my problem watching my Buckeyes against Oregon now.
That's surprising given the difference in pump length. Obviously good for others to know.
Fuel pump problem?
