1996 Volvo Penta 7.4 will not stay running

Socially D

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I have a 1996 Volvo Penta 7.4 that will not stay running. It cuts off after a minute or so. It does need some priming to get it going. I started at the fuel pump relay and replaced that first. Next I replaced the fuel pump. Still same thing. Next I rebuilt the carb. Same thing. Lastly I cleaned and inspected the distributor. Same result. Not sure where to go next or what I am missing. Fuel lines seem to be fine. HELP!
 

Scott Danforth

Grumpy old guy who plays with boats
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go back to basics
what is your compression?
what is your fuel pressure?
running for a minute and stopping is lack of fuel. i would look at the fuel pressure to confirm.

Volvo's get their non-cranking fuel pump voltage from the alternator.
 

Socially D

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go back to basics
what is your compression?
what is your fuel pressure?
running for a minute and stopping is lack of fuel. i would look at the fuel pressure to confirm.

Volvo's get their non-cranking fuel pump voltage from the alternator.
How can I check the fuel pressure during operation? I’m sure I could check it during initial start position prior to cranking. If that pressure is at 7 or 8 psi then I should be good on the pump. Since it is a new pump. I would think it is good. So, an alternator voltage issue then during operation? I can check pressure once I get a fuel pressure gauge.
 

Scott Danforth

Grumpy old guy who plays with boats
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A test port fitting and a mechanical fuel pressure gauge.

If you are reading 7-8 psi, it will open the needle and seat and flood your carb

However after cranking, if your fuel pressure drops, its either electrical or you may have a restriction in the line or your new pump may not be good
 

Socially D

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A test port fitting and a mechanical fuel pressure gauge.

If you are reading 7-8 psi, it will open the needle and seat and flood your carb

However after cranking, if your fuel pressure drops, its either electrical or you may have a restriction in the line or your new pump may not be good
There is no port or schrader valve. That is a bit more bothersome. Maybe the psi off of the pump is supposed to be 6. I’ll have to go back and check. I thought it was 8 max.
 

bruceb58

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Also, that distributor used in those things was only used for a few years and have known issues after awhile. I was proactive with mine and switched it to a Delco Voyager before mine went out.
 

Scott Danforth

Grumpy old guy who plays with boats
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There is no port or schrader valve. That is a bit more bothersome. Maybe the psi off of the pump is supposed to be 6. I’ll have to go back and check. I thought it was 8 max.
you are correct, there is no schroeder valve or other test port. it is a diagnostic tool.

you need to get a test adapter. such as this one

 

alldodge

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New pump
Put a voltmeter on the pump hot side and see if you get 12V to it while cranking?

Now see if 12V stays there once the key is released and motor is running?

If both are true and it still dies its either fuel restriction or an electrical issue
 

Lou C

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Also, that distributor used in those things was only used for a few years and have known issues after awhile. I was proactive with mine and switched it to a Delco Voyager before mine went out.
I think both OMC and Volvo used the Prestolite BID system for a few years but the modules for those are NLA so converting over to the Delco is about the only option.
I still have the Prestolite points distributor which for me is not really a problem since I grew up with cars that all had points. Did not get away from points till our 1975 Olds with the GM HEI system, our '72 Chevy and '70 Ford both had points.
 

bruceb58

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I think both OMC and Volvo used the Prestolite BID system for a few years but the modules for those are NLA so converting over to the Delco is about the only option.
Yes..since they were the joint venture years.
 

Lou C

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Yes..since they were the joint venture years.
I wondered if the Prestolite BID module could have been replaced with a Petronix? I've heard mixed things about those...thought about it but kept the points since I haven't really had trouble with them...
 

bruceb58

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I wondered if the Prestolite BID module could have been replaced with a Petronix? I've heard mixed things about those...thought about it but kept the points since I haven't really had trouble with them...
Why would you do that when you can just put in a Delco Voyager?
 
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