2000 MERCRUISER TBI 5.7 injectors quit at idle

[rhays001]

Good morning, Just got a 2000 230 Searay with a 5.7 TBI and bravo outdrive, 230 hours, no prior knowledge of how it ran other than said, "it needs a tune up". The motor appeared to run rich and had high idle around 1300-1500, but would run decent up to full throttle at 4600 rpm. Next day it would not start. Pulled coil wire and it had spark. Pulled flame arrestor and It is getting fuel pulse from both injectors when motor was cranking, but no start. Pulled plugs, (wet and black) changed them, and it would start again, rev fine, but again had a high idle high of 1300-1500 and appear to run rich. Checked the throttle linkage and found the throttle cable was adjusted to keep it at a higher idle. removed the cable to allow throttle body to be fully closed and the when the throttle closed, the two injectors immediately shut off. Found it will only pulse the injectors and start with throttle cracked open. Once running, it will rev fine, and injector pulse pattern increases strongly with more rpm, but as soon as throttle body is closed and rpm drops below 1000 rpm, the two injectors will shut off and the motor will stall. If i open the throttle when it is stalling, the injectors will immediately turn back on and the motor will run again.
I have never seen anything like this.
Thank you all for your help and advice.

 

[alldodge]

The old term it needs a tune up. Its used from needing a tune up to needing a rebuild

They may not be turning off, could be its just weak and not enough to keep it running. Maybe the fuel is old

Start with the basics
Check fuel pressure and will need an adapter 91-806901 and should be 30 psi at 1800 rpm. When key is first turned on does pressure come up and hold?


Check timing, compression, distributor cap and rotor

 

[alldodge]

Your TB may have a plug which pressure gauge can be installed. What is your serial number?

 

[rhays001]

Your TB may have a plug which pressure gauge can be installed. What is your serial number?

Thank you for your help.
Engine serial number 0L502971
I will get that adapter and get fuel pressure checked and will update you. I do not see a plug that I can attach a pressure guage to.

 

[alldodge]

The serial number is your drive
The TB looks like its showing the IAC and fuel pressure sensor. The fuel sensor can be removed and gauge gets attached

 

[rhays001]

Whoops
Serial number is
0L316174.
thank you for your help

 

[alldodge]

For me that's not helping. It comes up showing (where I think) the IAC is where the fuel pressure sensor is
https://www.mercruiserparts.com/bam/subassembly/31884/2704/110

I'm seeing this TB in the pic. Where the pressure sensor is item 10. At any rate we should be good to go forward
https://www.mercruiserparts.com/bam/subassembly/31886/4856/130

 

[rhays001]

While getting ready starting to pull the sensor to take the fuel pressure, I found a 2 prong plug with no where to plug into. I have another of these motors in a different boat that has the same harness with the cap covering this plug. It has a single wire that just seems to close the loop on this plug. I put that cap on this wire harness and the motor now stays running with the throttle body completely closed, however it now idles at 2000 rpm and will not lower. If I shut it off and restart, it will restart at about 1000 rpm and then immediate creep back up to 1800-2000 rpm. I can hear the IAC howling, Does this sound like a typical bad IAC stuck open?
thank you all again for helping me work through this, seems like these tpi’s always have more than one issue..
Attached are pics of the plug and the cap.

 

[alldodge]

What color are the wires and does the one plug go to the IAC?

 

[rhays001]

The plug that I put the “jumper” cap on is purple and black wires, These do not go to the IAC, the IAC has 4 thin wires of two blue and two green. I attached pics

 

[rhays001]

Was able to get the fuel pressure reading. I pulled that fuel pressure sensor and hooked up a guage, pressure when key turned on went to 30, When started ( still running at 1800 to 2000 rpm at idle) , it’s right at 30, Shutting it off, it goes down to around 28 and holds there with key off.

 

[alldodge]

Don't know what its used for. Was thinking the in gear switch but the colors are wrong and it didn't stat getting used until later

Your pressure is good.
Motor should be scanned to determine if there are any codes, other wise I would inspect the IAC. Remove a clean with soap and water, no chemicals like carb cleaner

With it removed, turn key ON and IAC pintel should move in and out then stop

 

[rhays001]

Don't know what its used for. Was thinking the in gear switch but the colors are wrong and it didn't stat getting used until later

Your pressure is good.
Motor should be scanned to determine if there are any codes, other wise I would inspect the IAC. Remove a clean with soap and water, no chemicals like carb cleaner

With it removed, turn key ON and IAC pintel should move in and out then stop

I pulled the IAC valve from the throttle body, plugged it back into the harness and hit the key. It didn't move at all. I will get a replacement in the morning. Thank you again for your help.

 

[rhays001]

Update
Replaced the IAC, it idles all over between at 600-800 rpm and is running very rich. Thinking it might be bad temp sender reading too cold , Replaced the temp sender (computer side ) and the map sensor with no changes
Have a friend with a diacom come over and and got 4 codes
22 throttle position voltage low
23 manifold temp sensor voltage high
33 manifold pressure sensor voltage high
34 manifold pressure voltage low

Cleared the codes and started it and it will start right up but run very rich, all 4 codes come right back
Checked the throttle position sensor with key on and cycled from closed to wide open and throttle position changed from 0 to 99.7% as it fully opened.
we have a reading of -38.7 degree F on the manifold air temp, so we replaced that sensor also ( the one that goes into the flame arrestor). And no changes stayed at -37 degrees
A pic is attached of the ecm data
Any thoughts on this are absolutely appreciated.
Thank you again for all your help.

 

[rhays001]

Update
Replaced the IAC, it idles all over between at 600-800 rpm and is running very rich. Thinking it might be bad temp sender reading too cold , Replaced the temp sender (computer side ) and the map sensor with no changes
Have a friend with a diacom come over and and got 4 codes
22 throttle position voltage low
23 manifold temp sensor voltage high
33 manifold pressure sensor voltage high
34 manifold pressure voltage low

Cleared the codes and started it and it will start right up but run very rich, all 4 codes come right back
Checked the throttle position sensor with key on and cycled from closed to wide open and throttle position changed from 0 to 99.7% as it fully opened.
we have a reading of -38.7 degree F on the manifold air temp, so we replaced that sensor also ( the one that goes into the flame arrestor). And no changes stayed at -37 degrees
A pic is attached of the ecm data
Any thoughts on this are absolutely appreciated.
Thank you again for all your help.

Another quick update, replaced the manifold air temp sensor with another new one and it is now reading fine at 72 degrees ( must have been bad). but motor is still running very rich
Thank you again for your help

 

[alldodge]

Looks like a voltage supply issue

Your battery voltage should be closer to 14V. Seeing 11.9V is close to a dead battery. Check output of the alternator once it revs to 1500 one time. Don't keep it there, just needs a quick bump

Check 5V reading at at the gray wire of the MAP, or CPS

The MAP is showing 29 Hg which would make it run rich. It should be reading less then that

 

[rhays001]

Thank you
Got dark out, i will do research on the map and take a measurement of voltage in the morning. Thank you again for your help

 

[rhays001]

Thank you
Got dark out, i will do research on the map and take a measurement of voltage in the morning. Thank you again for your help

Good afternoon, Back again
The voltage on the gray wire is 6 volts and does not fluctuate when the motor is reved.
Battery did Voltage goes up around 13 when the boat is at 1500 rpm
The map sensor when running is showing around 11-12 when at idle and goes up when reved, I attached a pic. I did check for vac leaks with carb cleaner and found nothing. Just for grins, I tried a different IAC from another motor and no changes, still runs rich.
Again, I appreciate all your help and ideas.
Thank you
Bob

 

[alldodge]

The 5V output is critical to the ECM and sensors. The 5V comes from the ECM and with it being high, either your meter needs checked or the ECM needs repair.

Check with another meter to verify

Your ALT needs to be repaired if the meter is accurate

 

[rhays001]

The 5V output is critical to the ECM and sensors. The 5V comes from the ECM and with it being high, either your meter needs checked or the ECM needs repair.

Check with another meter to verify

Your ALT needs to be repaired if the meter is accurate

thank you,
I will check and follow up.