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AznDrgn · Guest

I know someone on this board had this problem before but I can't find the post anywhere. I've got lots of pressure in my fuel tank and I can hear my fuel pump screaming. I've changed all the filters, pre pump filter, and the one in the engine bay. That got the pump to run correctly for a little while but then about 30-40 miles down the highway I feel the engine surging like there is a lack of fuel. I pull over and the pump is screaming again, I checked the filters and they are all still fine. I remembered a post about pressure in the tank so I opened the cap and a LOT of pressure came out and the engine died. After all the pressure came out I started the car up and it ran alright but the pump was still quite loud. I drove about 4 miles home opened the cap again and there was pressure again. The cap I have is good, it was just pressure tested two weeks ago when I got my emissions testing done. I have no other ideas on what is wrong, if you have any please let me know.

Thanks
Danny

P.S. This is on a '78 924 NA I think the PO swapped the engine to a '79 though.

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2743 Location: Sydney, Australia

positive or negative pressure? (did is suck or blow when you took the cap off).

AznDrgn · Guest

Positive pressure, it was blowing out.

wdb · Guest

is the gas cap supposed to vent the pressure , like most cars . does the car run with the cap off . is your exhaust system over heating your gas tank ,too close or missing heat shield .

AznDrgn · Guest

I think the cap is supposed to vent and if not there is a line that goes to a charcoal canister that should vent it. My exhaust doesn't overheat as far as I know and it has all the proper heat shields in place. I don't know if it runs with the cap off or not but I'll go try in a few minutes.

AznDrgn · Guest

yes it does start and run without the gas cap on.

924RACR · Posted: Mon Aug 05, 2002 10:02 pm Post subject:

The tank vents through the charcoal canister, not the gas cap - emissions. Sounds like the vent hose running up front is kinked or plugged. Sounds like you may also have fried the pump pulling on vacuum, if it's making that much noise.

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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
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wdb · Guest

I wonder if the high tank pressures helped the fuel pump and raised the fuel pressure and caused you to run rich and fail your emmissions test .

jcope · Guest

The other discussion on this topic was at
http://www.924board.org/viewtopic.php?offset=&topic=196&forum=1

AznDrgn · Guest

Hmm I'm confused now. You all are saying that it could be the charcoal canister, but I've been running the car fine for the past two weeks and this is the first I've seen of this problem.
Now on the other post it says it was the small valve that is mounted on the fuel distributor that controls fuel pressure for start up.
Well guess I'll be doing some trial and error work tomorrow. Anyone know where the charcoal canister is located? Is it the one inside the drivers side fender? and where does the vent tube come off the tank?

Thanks

MBENGOLEA · Guest

A learnt that noisy pump means broken pump. I suggest you have tested your pump by a serious mechanic.
Have luck,
Miguel

AznDrgn · Guest

I've solved the problem!!! I drained the tank and opened the access panel and there was trash and rust clogging the outlet line. I cleaned it all out put a fresh filter in before the pump and now it runs fine.