5.7 Volvo Penta lean popping

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Feb 22, 2018
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Hi all, I'm new to the site and have a tech question. I have a 2000 Volvo 5.7 GI. The problem is when first started for the day the engine will run fine for approx. 20 minutes. Then there is a pretty violent lean pop in the intake. If I don't pull the throttle back and shut it off it will eventually shut off. If I let it sit for a few seconds it will start back up and run fine for a few more minutes and happen again. After sitting all night, the next morning I can start it up and run again for apprx. 20 minutes and here we go again. I have the diacom software and have watched all the data as it's running normally and then when my problem arises. I don't see anything out of sorts. The fuel pressure on top of the high pressure pump is 31 psi. It doesn't fluctuate when my problem arises either. I pulled the injectors out of the throttle body and had them cleaned and serviced. Did not help. I've tried running a separate fuel tank. I've replaced ignition coil, distributor pickup, cap, rotor, wires. plugs, map sensor, tps, and IAC. Nothing seems to help. Now that being said I have access to another Volvo of the same year but with a 5.0 GI. I pulled the throttle body off that one and put it on my 5.7 and it does the same thing, but the lean pop is not as violent and the engine will continue to idle without shutting off. I'm not sure if the 5.0 and 5.7 have the same injectors or not? Any thought from you guys? I'm kinda at a loss now
 

Lewis1111

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What is the history behind the issue? Did it just start happening or after something else occurred? Seems to be related to when the engine starts to warm up....Have you done a compression test? I would do one with a warm engine.

Also what do the plugs look like right after this occurs?
 

alldodge

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lean popping

fuel pressure on top of the high pressure pump is 31 psi

I would do a compression test. Think maybe you have a valve not closing
 

alldodge

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Also check timing, if its way off can cause similar issue
 

Scott Danforth

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sounds counter intuitive, however have you cleaned your distributor cap contacts and rotor contacts. long story, however highly recommend checking under the dizzy cap.
 
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Thanks for the responses! The compression is good on all 8. I usually run the boat at around 3000 rpms. If I run it under about 2200 it doesn't seem to have the issue. I've owned this boat for about 7 years and this problem just started last year. No other running issues. The timing is correct, I've checked with a timing gun with the engine is service mode. I feel that I'm pretty good at diagnosing and fixing mechanical things, but now I'm not so sure.
 

alldodge

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replaced ignition coil, distributor pickup, cap, rotor, wires. plugs, map sensor, tps, and IAC

So everything is spot on and nothing is wrong, fuel pressure is great, been throwing parts at it the problem and still have a lean pop.

The fuel pressure on top of the high pressure pump is 31 psi. It doesn't fluctuate when my problem arises either

Most cases this is caused by a reduction if fuel, but your at a constant 31 psi

Only thing left in my opinion is either a bad connection with power, a ground or ECU.
 
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Feb 22, 2018
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Alldodge, I agree. everything seems good. I've wondered about getting a wiring harness for it. I have a friend with a Regal with the same engine. I even tried his ECU and the problem was still there. I'm to the point of a wiring harness or possibly a valve issue somewhere, but I would think if I had a valve problem the problem would be there more. Especially since it seems to be temp related to a certain degree. After the engine warms up I would think the issue would be constant, not come and go. But at this point I sure don't know.
 

alldodge

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You had the injectors cleaned and tested, can I ask by who?

Want to find out if they were tested for flow and pattern up to 5000 rpms.
 

Shaper79

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Lake Sinclair Greg. ., do you mind if I can ask. What your timing was set at.
 
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AllDodge, they did give me a printout showing spray volumes at certain rpms and pressure's. I don't know about the baskets though. I don't have that sheet anymore so I can't tell you specific numbers. But I remember looking over it and they gave bot injectors a "pass" whatever that means.

Shaper79 I set the timing at 8 btdc in service mode
 

alldodge

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You know I might be heading in the wrong direction because of the term "lean pop". This leads me to think its is actually running lean where it might be a miss. It's a light backfire, correct?
 
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Yes it is a backfire through the intake. I have always thought of those as a lean pop because usually that type of back fire is caused from a lean condition I thought. But I wouldn't call it a light backfire. It's a pretty big one with no indication whatsoever that it is about to occur.
 

Shaper79

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Ok. Cause I have the excact same motor. I thought it was supposed to be set a zero. I wanna check mine. Could you give me the steps. To check timing.
 
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I use the diacom software to put mine in service mode. There is a procedure to do it without the computer but I'm not exactly sure of what it is. You have to either ground a certain wire off the distributor or give it 12 v. That locks it in service mode. Then I just set it like normal at 8 btdc at idle
 

alldodge

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It has to be lean fuel

There has to be something missing
 
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What do you think are the chances of an injector getting hot after running at shorting? I did bolt on a complete throttle body from a 5.0. Do you know if the injectors are the same from 5.0 to 5.7? I still had a backfire with the 5.0 throttle body, but it was not as violent as with the other one. I'm wondering if maybe the 5.0 injectors weren't giving me enough fuel and that's what caused it with them. Maybe I fixed the problem but caused another one with smaller injectors?
 
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