Need fuel system help, Please!

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Old Frog

6/2/2007 8:03:22 AM

Good Morning. Please allow a question from a newbe. This problem is getting the best of me.

The vehicle is a 1997 Safari Van AWD, 4.3 with a CSFI fuel system. 155K on the clock. I have owned since 15K & the maintenance has been good. The van has an intermittent no start problem fuel which, I am thinking is a result of low fuel system pressure.

My previous diagnostic efforts lead me to replace the in tank pump with a new Delco unit. The tank was cleaned. A new filter was installed. The pressure was still low. A return fuel line restricting valve test done (pressure from the in tank pump to high high 60's (I did not push it higher)) indicated a faulty fuel pressure regulator. A new fuel pressure regulator w/ screen & o-rings installed was installed. Currently the engine runs & operates fine once started. It restarts fine when warm. The engine runs great once running. - No CELs are displayed.
- There are no visible leaks. No visible kinks or restrictions in the fuel lines. - Fuel pump relay & electrical system components all appear fine. Key On, Engine Off, pump cycles & pressure builds to approx. 52 PSI. Engine will start with a shot of starting fluid & continue to run & drive fine after that. Warm restarts are immediate. Cold restarts the following morning do not happen. I have driven the van around with the engine box off watching the fuel pressure gage. From a cold start: - System pressure reads 0. - Key On, Engine off, Pressure builds to approx. 52 PSI, but the engine still will not start. Starting fluid is needed to start. - With engine running & in normal driving, pressure gage readings range in the mid 50's to low 60's. Idle is in the low 50's with an occasional dip to about 48 or 49. - Engine turned off. The gage reads about 55 PSI & holds up to several hours. Warm restarts like this are not a problem. - Over night, the system pressure drops to 0 & the above cycle repeats. My Haynes manual states the spec is: Key On, Engine Off: Approx. 55 to 61 PSI Engine Running: Pressure should decrease by 3 to 10 PSI. Thus, I am thinking it is a low pressure problem of some type. Something that prevents the pump from building the pressure @ a cold start. I am starting to get POed by this time. Any suggestions on where to look next or how to proceed from here would sure be appreciated. Thanks in advance. Bob

97benzman

6/3/2007 7:22:42 AM

i know this may sound a little off, but with all the parts u say u have replace, have u re-booted ur engine control unit by disconnecting the battery ground cable?

Old Frog

6/3/2007 9:41:06 AM

Thanks for the input. I did reboot & idscharge the residual charge.

At this point I am beginning to wonder if it is a sensor malfunction @ cold start that is throwing off the fuel/air mixture or perhaps timing. Or event the CSFI to MFI fuel system tsb issue. I have read some on that, but syptoms do not fully match. Mine is a cold start with a smooth idle while the tsb mentions warm starts & rough idle.

Any more ideas or sugestions would sure be welcome. Bob

BigBoom360ci

8/6/2007 9:26:18 AM

Have you thought about the injection parts being non effiecient enough from being 10 years old?

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