5.0 GXi-A Fuel pressure drops immediately after key off.

[callen369]

I have the TBI motor, and when doing a recent fuel pressure check to troubleshoot my hesitation problem, I noticed the fuel pressure drops as soon as the pumps stop. Question is, should it be happening on this system? I know it has a return line, but I "assumed" it should maintain a certain level of fuel pressure in the line after the motor is shut down. It drops to 0 in a matter of seconds. Is this a sign of a bad fuel pressure regulator?

My fuel pressure from low side is around 14psi, and from the high side 34psi, and does not fluctuate but 1 or 2 psi under load and sudden throttle movements or WOT.

Thanks

 

[Fun Times]

Hi there, No the fuel pressure should be holding after key off.....Also looking up your fuel pressure specifications, your a bit too high. Low psi should be 8 +or- 4 while the high is 29 +or-2. http://boatinfo.no/lib/volvo/manuals/5057a-f.html#/166

Typically a quick drop in fuel pressure after key off would be a regulator problem or injector problem. Being a TBI, you should be able to see easily if the TBI injector/s are leaking.

If you do an online search for Volvo Penta paint inside the fuel cell, it should help give you many ideas of other things to check on your fuel system while your in there inspecting.

You may need a new regulator or cleaning the fuel cell and regulator system may just help as well. The fuel pump screens sometimes need a cleaning too.

Let us know what you find, good luck.

 

[callen369]

Regulator it is then....I have been completely through the fuel cell in the last month or so, cleaned screens, etc. Been through the throttle body to clean it, replaced rings and screens on injectors, and the regulator looked ok, clean anyways, and the spring was a pain to compress , and put back together.

The gasket kit I purchased came with a diaphragm, but I couldn't get it not to leak, so I reused the old one. I am having trouble locating a volvo penta specific diaphragm and spring, are these the same as the GM throttle body parts I can pickup at NAPA? I don't normally like to purchase non-marine rated components...


Also, not sure if you know much on timing....but I have read about setting base timing using a special "plug" adapter on my distributor...but, the plug that most people are talking about on mine is occupied, and goes to the coil, I think. Am I supposed to disconnect from the coil and then set it? Right now, I have the balancer mark lined up on compression stroke, Distributor inserted and aligned with original marking on manifold, and the rotor points to #1 plug wire. Anything else I need to do, or should the base be set close enough already?

 

[Fun Times]

Both Volvo and Mercruiser fuel regulator part number is 852955 which is no longer available and the GM part number is 17112399 which I believe is fading away now.

Run the number through ebay, there are 4 listings right now.

Earlier I was thinking of a regulator being lower down near the fuel pump area letting the fuel flow back down to the pumps not up at the throttle body. Should the regulator be bad at the throttle body, I believe it would only dump fuel into the body like it did to this guy. http://www.offshoreonly.com/forums/general-boating-discussion/193042-mercury-575sci-help.html But I could be wrong also.

You may have a bad fuel pump allowing the fuel to flow back down. Some EFI fuel pumps have a check valve inside the pump that only allow a one way flow. Your valve may be stuck open. Just thinking out loud here for you is all. http://www.google.com/url?sa=t&rct=...-oGYBA&usg=AFQjCNEA-P6wjGckq3LvjFwX3SrqW7lMNg

Does the engine take longer to start now since there is no fuel pressure at rest? It should start within say 5 seconds with everything working correctly.

 

[Fun Times]

Also, not sure if you know much on timing....but I have read about setting base timing using a special "plug" adapter on my distributor...but, the plug that most people are talking about on mine is occupied, and goes to the coil, I think. Am I supposed to disconnect from the coil and then set it?

Since you have a TBI which = fuel injection, the way you achieve base timing mode is you either use a Rinda scan tool, Code Mate MEFI Code Reader or jump pins A and B at the data link connector. http://www.rinda.com/marine/marine.htm#codetool

See the bottom half of this link (V6 and V8 EFI Models EFI Ignition)
https://www.google.com/url?sa=t&rct=...XQ4Qqxxb4JYu6Q

Here's a video of the data link connector for you to see to get familiar with: https://www.youtube.com/watch?v=s2GEO-dlbIg

The carbureted models would utilize the plug at the distributor like your asking about.

Hope this helps, good luck.

 

[dypcdiver]

You also might just find it under this number ACDelco #217-389

 

[callen369]

Thanks guys, much better. I guess I was looking at the carb procedures.

So, I have the TDC compression stroke lined up, white marks on dist. base lined up, rotor is pointing at plug wire 1. Now I just need to put my timing light on, and jumper the 2 pins to set base @ 1800 RPMS.....doesn't sound too bad.

From the pictures on the site, it looks like the plug is the one by my breaker on the starboard riser....Yes?

Will wait until I get the headers and risers on though....something about loud, hot exhaust and water in my engine compartment...just doesn't sound like I good idea...

Please correct me if I am wrong on anything above.

Thanks again.