2002 Tahoe 202 - Mercruiser 5.0 MPI fuel pump not priming

[ZLJUANN]

Does the pressure stay up or come back up after it starts?

The day we tested it stayed up.
i found this post that pretty much describes exactly what’s happening but there was no resolution.


https://forums.iboats.com/forum/eng...536-mercruiser-5-0-mpi-delayed-ignition-alarm


i tested voltage across what I think is the ECT and got 5v and 12v across the IAC. Is that correct?

also, at cranking I get 0 psi at the oil pressure gauge at the dash. When it sputters wanting to start up, the gauge shows around 30-40 psi. Is that normal?

 

[alldodge]

i tested voltage across what I think is the ECT and got 5v and 12v across the IAC. Is that correct?

also, at cranking I get 0 psi at the oil pressure gauge at the dash. When it sputters wanting to start up, the gauge shows around 30-40 psi. Is that normal?

Both would be normal

 

[ZLJUANN]

Both would be normal

Copy. Here is the link to the post I was referring to. I timed it and the alarm timeout is more like 20 seconds not 6 seconds.

https://forums.iboats.com/forum/eng...536-mercruiser-5-0-mpi-delayed-ignition-alarm

 

[alldodge]

Merc has a timed and non-timed alarms.

You can get a straight alarm or one with a timer as part of the alarm.

Many of the higher priced boats get the timer so it gives 20 seconds are so before its sounds off. My Formula has one, but my Rinker does not

 

[ZLJUANN]

Merc has a timed and non-timed alarms.

You can get a straight alarm or one with a timer as part of the alarm.

Many of the higher priced boats get the timer so it gives 20 seconds are so before its sounds off. My Formula has one, but my Rinker does not

Well I suppose this is a timed alarm system.
I tested the ignition system yesterday. The ignition control module fires off strong. Has the right voltage in the right wires etc.

im stumped. Good ignition, good fuel pressure, good air intake. Since I get clean 5v and 12v that means likely sensors are all good so I don’t know what it would be seeing that it doesn’t like.

ECM refusing to connect to Diacom diagnostics sucks. Checked for voltage at the DLC and I have good 12v and ground. Just won’t connect to the ECM.

 

[alldodge]

There are 2 other connections

 

[ZLJUANN]

There are 2 other connections

Sorry, are you saying there are 2 more connectors where I can plug in? Or to test signal at?

for the DLC, does the ECM supply voltage to the connector?

 

[alldodge]

Sorry, are you saying there are 2 more connectors where I can plug in? Or to test signal at?

for the DLC, does the ECM supply voltage to the connector?

No, I'm saying there are 4 wires that need to connect for the scanner to connect to the ECM. You mentioned Rinda wasn't connecting.

 

[ZLJUANN]

No, I'm saying there are 4 wires that need to connect for the scanner to connect to the ECM. You mentioned Rinda wasn't connecting.

That’s a fair point. I didn’t test that. I remember from integrated circuits course way back in school that traditionally they are 5v pulses. Do you know if that is accurate for these?

 

[alldodge]

That’s a fair point. I didn’t test that. I remember from integrated circuits course way back in school that traditionally they are 5v pulses. Do you know if that is accurate for these?

Don't know for sure but most likely it is using TTL.

 

[ZLJUANN]

Don't know for sure but most likely it is using TTL.

So pins A: 0v
B: 5v constant
C: 0v constant
D: 12v

so it seems pin B is data down and pin c is data up and it’s just stuck. I went from my Volvo instant connection, ran to the Merc, switched the ecm type in the software and tried to connect and nothing.

 

[alldodge]

I would ring the wires out, if they ring out then its not the wiring.

If its not the wiring then may want to contact boatsunlimited to see if they can test it

 

[ZLJUANN]

continuity was fine on the wires. found this place searching around. They are about an hour from me, even closer than Whipple and its only 50 bucks to diagnose and 625 to repair. Going to take it in just to rule that out.

https://www.simonperftech.com/products

 

[ZLJUANN]

Just to round this one up and put some closure.

Got the ECM back today after repairs. Boat fired right up and hooked up to DIACOM. Cleared the codes and ran great on the muffs. Looks like the 120 degree havasu heat killed something internally.

Monitor to see if any codes come back.

 

[alldodge]

A two day turn around that's great. I'm going to make a note about these guys for future reference

 

[ZLJUANN]

A two day turn around that's great. I'm going to make a note about these guys for future reference

Yup they were great. They used to be called just Simon motorsports i believe. I found them on this forum and after some googling I found their name change.