Need help with Vapor Lock issue
 

Well, I have an '82 Excaliber 38' with 2x 541 BB MEFI-1 engines in it. The port motor is fine. The starboard motor, which also runs my power steering pump, has an issue. It starts fine when cold or below 120deg. If I get it up to temp and shut it down, it won't start. I know the timing is dead on where it should be and every part of the fuel delivery system (2x pumps per motor) has been replaced to include all the lines.

Somehow, I think I'm getting vapor locked. I know it's not a false overheat code because I swapped the main computer out with a spare and that problem went away. Is it most likely vapor lock or could it be something completely different. As soon as it gets below 120deg it'll start right up and run great.

Swap the ECM and the problem goes away. This tells me its the ECM

Vapor lock takes time and heat. Your issue is instant as soon as motor is up to temp and shut down. Unless I missed something

It doesn't shut down on it's own. Once I shut it down for whatever reason, it won't restart until the temp drops to 120 or lower. Here's the thing, my gauge in the dash and the code reader both indicate at Idle I'm not getting past 150deg, so i know it's got plenty of water flow, gaskets are good, and it's not over heating.

Got it, but did the problem go away when the ECM (computer) was swapped?

who programmed the ecm's , what efi are you running

What problem went away ?

Please be more clear on things so we can follow and help easier.

So, did you check for spark and fuel psi when this no start happens ?

The false over heat code went away, but not the starting issue when engine is at running temp.

As for the ECM, they are the MEFI-1 and I don't know who programmed them. I did send the spares off to have the original starboard side fixed and both reprogrammed. Sent detailed specs of the engine builds along with them, too.

Thanks
When it won't start
Can you hear the fuel pump prime?
If yes, what is the fuel pressure reading (VST would be 37, but yours may be different)?

With key ON is there 12V at the coil during cranking?

Both pumps on this engine prime and are new. One gets it from the tank to the main pump and the main, well...sends it to the rail. I have two batteries per engine and all are new. Voltage is where it should be for the coil and that is also new. Fuel pressure is a constant 45psi. I have also checked for spark and am getting that, too. The TPS is also set correctly and reading the correct voltage, too.

Only thing I can think of is there's a problem getting fuel into the cylinders after the engines are warmed up and I shut it down for whatever reason.

SB, the false over heat code went away when I changed the ECM, but the no start problem still persists.

what EFI are you running asking again

mefi-1

thats the ecm, is it TB EFI.........502 mag mpi ?? 500 EFI

Throttle body EFI, Tune port injection. These are the best pics I have for now.

https://scontent-atl3-1.xx.fbcdn.net...30&oe=60C210DE
https://scontent-atl3-1.xx.fbcdn.net...5a&oe=60C06A12
The engine bay was going througha big cleanup in this pic.
https://scontent-atl3-1.xx.fbcdn.net...72&oe=60C1C063

Custom MPI setup
Since your getting spark and have fuel pressure, something is telling the the ECM to not turn ON the injectors

Normal for a MEFI-1 with Merc program
Once the ECM see's that the distributor is firing the spark plugs, then it will turn ON the injectors. They injectors are batched fired so have fires then the other half.

Your getting spark but can you see the tachometer show at least 300 rpm while cranking?
If it shows 300 rpm or more then the ECM should be turning on the injectors

If somehow it is vapor locking, you can releive the VL by pressing in on the fuel rail schrader valve. Use a rag and safety glasses and press in to see if you get nothing but fuel, or there is some air

thanks. I'm going to look into the ECM some more. I did hit that valve and fuel shot out. Valve for this set up is on my main pump, though.

It still makes no sense why it would shut down the injectors after getting up to temp?

D'oh!!!!! 8 bad injectors and I could see where they were leaking going into the manifold. Guess what.....16 new injectors are on the way and the 8 good ones from the port motor will be kept as spares. When I hit the shrader valve, fuel would shoot out, but over the course of 10-20 minutes my fuel pressure would drop to 15 psi and it's never done that before.

The ECMs came back from repair and reprogramming yesterday, so I'll put those in along with injectors, cross my fingers, and hope I don't need to commit insurance fraud to fix this issue with a small can of gas and a match.

Wishing you a long and trouble free season.

Thanks. This boat has been one nightmare after another, it seems.

8 leaking injectors?? Sounds like your fuel sys is contaminated.

Not sure abt your setup, but some of the fuel inj Mercs had an issue with paint coming loose contaminating the fuel sys. I think it was in the cavity where the hp pump resides.
Regardless, you better get the fuel sys sorted out before installing new injs.

Do your injectors have screens on the inlet? Were they dirty?

Sounds like you have some other issues, but I had a friend with a 400SS with gas motors in it (believe they were MPI motors) and he would experience vapor luck with winter blend fuel. He would always have to wait until after the summer fuel was brought to the marina before he filled up...

They had the screens and the only thing I haven't replaced in the fuel system on both engines would be the injectors. Everything else including the hoses are new.

A couple of them had small hairline cracks, too. Better to just eat the cost and replace them all while the mistake...er..boat is still on the trailer.