Port engine occasionally hard to start

F

firecadet613

Well-Known Member
May 10, 2007
5,253
Indiana
Boat Info
SOLD - 2007 Four Winns V358
Engines
Twin VP 5.7GXi V-Drive / ZF63s
I've been dealing with this issue for two seasons now and thought I had it resolved until it happened yesterday morning.

I have twin Volvo Penta 5.7GXi's with just over 700 hours. Both motors run well, burn no oil and perform well. They were last tuned up in 2017 (planning to do that later this year).

The starboard motor always fires right up, the port motor occasionally will die as soon as I release the key. Cranks fine, seems to fire up fine, but dies as soon as I release the key from the start position. It is throwing no codes and all appears to be normal based on the readings from my Fox Marine Gateways. Last year I tried a new IAC, no change. I cleaned the MAP sensor and that seemed to do the trick, until yesterday morning.

For shits and giggles, I tried to start it last night and she fired right up. Same as this morning - fired right up. Any ideas what to check?

It hit me this morning I wonder if it's my ignition switch (which would be a major PITA to change, given it's location and lack of access...
 
I'm thinking it's not my fuel pump as sometimes it fires right up and there is never an issue once it's running. Does that mean I can take out the ignition switch as a possible cause as it never happens once it's running?

Surely someone has had this issues on a Merc....
 
I would rule out the ignition switch since as long as the starter is turning, it did its job!

So to confirm, when this happens it will crank/turn over but just not run? Or are you saying it starts to run but then dies when you back off the start button?
 
Phil S said:
I would rule out the ignition switch since as long as the starter is turning, it did its job!

So to confirm, when this happens it will crank/turn over but just not run? Or are you saying it starts to run but then dies when you back off the start button?
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Cranks / turns over but will not stay running. Once I let go of the key, she dies. But then other times she will start up just fine.
 
Intermittent starts are hard to diagnose.

It sounds like this is always a cold start?

In the case of cranking but not firing I would lean towards spark or fuel.

Normally if you suspect an ignition switch, I'd say swap them and see if the problem goes over to the other engine but you mentioned that they are hard to get to?
 
Phil S said:
Intermittent starts are hard to diagnose.

It sounds like this is always a cold start?

In the case of cranking but not firing I would lean towards spark or fuel.

Normally if you suspect an ignition switch, I'd say swap them and see if the problem goes over to the other engine but you mentioned that they are hard to get to?
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Yes, hard to diagnose and a PITA LOL. It was given a full tune up in 2017 per the receipts I have (and I have all the parts to do one later this year). Fuel appears to be ok as there is no issue when running and the fuel pump cycles normally (I gave it a few on/off cycles to ensure it built pressure before starting - but that seems to have no effect at all as it would start on the first turn of the key at times).

scoflaw said:
"once I let go of the switch it dies" a very telling clue.
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Telling, but I'd expect it to happen more often than not? No issues when I launched (but 2021 launch it acted up and I had them throw their computer on it - no codes or anything that they could find) last weekend it started right up just fine, Sunday night and Monday morning just fine. But Sunday morning, I'd crank it (sounds normal), but it would not stay running. 4th try, it stayed running.

I had some success last year after I cleaned the MAP sensor - I plan to swap it with the starboard engine next time I'm up and see if the problem travels to that engine. Others have suggested the crank sensor or like you and @Phil S are leaning towards - the ignition switch.
 
firecadet613 said:
Others have suggested the crank sensor or like you and @Phil S are leaning towards - the ignition switch.
Click to expand...

Now that you mention it ....

I have heard of this happening with the crank sensor. I've seen the same thing happen on a TPS on cars where they develop a dead spot. When you cleaned the MAP sensor last time, how long before the problem returned? You might be looking at a loose or dirty connection somewhere.
 
Phil S said:
Now that you mention it ....

I have heard of this happening with the crank sensor. I've seen the same thing happen on a TPS on cars where they develop a dead spot. When you cleaned the MAP sensor last time, how long before the problem returned? You might be looking at a loose or dirty connection somewhere.
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Looks like it was fine from mid-July to haul out in October...but that's one thing I didn't clean out - the connector itself. I'll try that this weekend as well...
 
370Dancer said:
check your battery voltage. EFI's hate low voltage.
Click to expand...

They are 5 years old and likely on their last legs - my engine hatch was painfully slow to lift up today!

Frigging MAP sensor. Pulled them to swap engines and ended up cleaning them again. No issues after a few starts. I'm buying a spare to keep on board.... but it looks like they fogged my EFI motors!

I have no other way to explain the oily film on my flame arrestors, under the engine cover and on both MAP sensors myself. Glad I moving to heated storage this year with no one being on my boat but me, myself and I!

Time will tell, but my initial observation is that's it.
 
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