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| Re: Ported EFI problem [message #238909 is a reply to message #238900] |
Wed, 05 February 2014 17:21   |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| Bobby Lee wrote on Wed, 05 February 2014 16:58 |
1978 Royale coach came with a "Digital Fuel Injection Inc" for a tuned port injected engine on a 403. There are two electric fuel pumps, one centered on a frame cross piece and the other on driver side rail. Manual says system operates at pressures up to 50 psi.
Symptoms are cranks but will not start. At other times starts immediately. Oddly enough when jacked up on driver side, starts right away. Guys at rally said jack it up and start it every time!  John Sharpe is helping me to fix the problem, but, if anyone has a similar system, would appreciate input. Thanks
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I did see a similar issue with a mule (vehicle with an old body on a new chassis to do over the road development). It would lose fuel pressure and stop at the most inconvenient times. It turned out to be a bad ground to the steel fuel tank. The tank would shift at times an come un-grounded. Now, I want you to think that I found this right away and didn't tear out any hair or get angry.
I would suggest that you listen for the fuel pump. If you can't hear it all the time, run a single ground wire to someplace you know is a good ground.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Ported EFI problem [message #238960 is a reply to message #238900] |
Thu, 06 February 2014 09:41 |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
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Can't speak to this specific brand, ony in FI generalities:
First, is it a tuned port system [never seen one for Olds] individual port injection [adapting to existing manifold ? or Throttle body? {like a repacement carb]
Im going to guess that it is not TB as the pressure on those is usually much lower [although not on my Air Sensors system]
What you need to know is what the fuel PSI is: Static, then when the key is swiched to on [pump should run briefly to presurize the line], during start up and then while running.
On the fuel rail somewhere is a Shreader valve that you can check pressure with an inexpensive gauge [harbor Frieght!]
Most systems use a bypass regulator that returns fuel to the tank . Some systems deadhead into the rail.
It sounds like its not presurizing at start up or has a regulator malfuntion [bypass sticking open or bleeding off= static psi low or 0.] I assume you have ruled out an ignition problem?
I would recommend a dashmounted electronic fuel PSI gauge for anyone running FI.I am going to put the airsensors kit on mine that I used to run on my Trans Am 406, but wil carry the Qjet and parts needed to revert on the raodside if need be.
76 Glenbrook
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| Re: Ported EFI problem [message #239068 is a reply to message #238960] |
Fri, 07 February 2014 09:35 |
corleyw
Messages: 130
Registered: June 2007
Location: Battle Ground, WA
Karma: 0
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This is not really a "Anyone else having this problem" type of thing. You simply have to do the analysis of the failure. IE: When it fails, does it have spark? When it fails, does it have fuel pressure? When it fails, are the injectors getting signal to fire? ETC. Shot gunning is only good for some problems, not all problems. If there were thousands of systems exactly like yours installed on GMC MHs out there, perhaps some of other peoples experiences would apply, but not so much here.
That's the bad news. The good news is it is really not all that complicated a system for a knowledgeable person to analyze.
JMHO
Corley
'76 Glenbrook
29 other vehicles
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