Losing Fuel Pressure

jackmech · 10-08-2002, 08:59 PM

I am doing a bunch of testing on my recently "rebuilt" engine and I noticed that I was losing fuel pressure after turning off the engine/fuel pump. I checked all the injectors including the cold start (who put that thing there! SHEESH!) and none were leaking. So I pumped up the pressure and clamped the supply line and low and behold it looks like the check valve on my fuel pump is failing/has failed. My question is, will this cause problems for me? It still starts right away and I can't imagine that it would cause a problem, but I don't know everything.

Of course if I do have to replace the pump then I'll be able to use this one for my planned bench top fuel injector tester. Thanks!

WOODPIE · 10-08-2002, 09:58 PM

jackmech

I don't know everything either, but if your car starts fine, I wouldn't worry too much. I've read the check valve is there to prevent vapor lock, and allow for easier restarts. I don't think it was ever too successful with the vapor lock issue, as the pump was eventually relocated. Your car starts right away, so the pump apparently is in good shape otherwise.

Ed

jamcleod · jamcleod's Garage

??? i have a question. i have a 74 1.8 but i don't remember a check valve for any pre 75-76 914. not that familiar with 75-76 but when they moved the fuel pump to the front, i vaguely recall a change in the fuel pump used, that is, 70-74 is one and 75-76 is different (like a 911 f.p. my 83 has a fuel pump with a check valve.) still, i don't think yours normally would have a check valve (normally=if stock, no PO did modifications, etc)

jackmech · 10-09-2002, 06:49 AM

In order to test residual fuel pressure for D-Jet, as described in FI manuals and 914 books, there would have to be a check valve on the pump. Otherwise you wouldn't be able to test residual fuel pressure. I think a lot (all?) of fuel pumps have them internally, non-replaceable. Which reminds me, that I've relocated my pump and use the later style single-in/single-out pump.

pbanders · pbanders's Garage

The check valve on the pump helps hot restart. If you're not having a problem, I wouldn't worry about it too much, as long as you're getting a stable 29 psig pressure when it's running.