pier3pressure

I'm running twin 1994 454 Mag EFI engines in a 29' PowerQuest Enticer. When cold both start great and run fine for a long period of time. After shutting them down and waiting an hour or so the starboard engine would not start up again. Or it would start hard and when I give it gas it will bog down and die. Mechanic diagnosed the problem as “vapor locking” and the ECM was fried therefore we needed to replace the ECM. After replacing ECM the problem jumped to the port engine and did the exact same thing. Again we replaced the ECM and both worked fine, until we had to idle for a long period of time (no wake zones) The problem has resurfaced again this season in the port engine. If I’m fortunate enough to get it started it will not rev past the idol without making a pinging noise. Sometimes you can feather it to get it going and then it seams to work it self out. I should mention that I can here a whistle sound just prior to the engine shutting down. Idles at roughly 500 rpm. Not sure if it is starved for gas or air? Any help would be greatly appreciated!

Poorsche

Check the fuel pressure regulator--that was culprit when I had similar problem.

Trippin

MAP, IAC, TPS, ECT, MAT, a thorough check of these components is in order on both motors B4 you go and replace any more ECM's !

Poorsche

Have you uses a RINDA tester yet to look at all the diagnostics and data from the ECM?

5 bucks to a donut it's not an ECM failure as Trippin suggested. \

Also--all the parts Trippin suggests are standard GM parts and a good (not Poop Boys or Discount) can cross-ref for you.

Poorsche

Jerry B

I have a 93 Fountain W/twin 502s. Same fuel system. Your problem sounds just like mine. Both start fine cold but port side is hard to start after hot. I have to apply some throttle and several seconds of crank time before it will start. Mine runs fine after it's started thou. No problem untill next shut down and restart. I think it's vapor lock too. I bought two fuel pressure gages. One for each engine but I havent come up with a way I like to adapt them in the pressure line after the electric pump or at the rail. I thought I would remove the schrader valve and get a fitting to go there that I can adapt the gage to but the fittings would be pretty small and I'm afraid there could be a failure causing a fuel leak. I may have a new line made with a T to put at the VST. Anyway I think what happens with mine is the fuel boils in the VST. Then at key up there is no fuel for the electric pump to push to the injectors. Then after several seconds of cranking the mechanical pump has resuplied the VST and then the engine will start. If you do a search here on vapor lock you will find several post about this problem.
Sorry for being so long winded. I beleive the next thing to do is make sure there is fuel pressure at key up. I'm a GM auto tech by trade and beleive me. It's easy to blame all sorts of electronic gadgets for any number of porblems. Dont overlook the basics. No matter how sofisticated the systems are no engine will run without fuel.
Good luck getting it fixed.