98 Merc 150 EFI 0G74xxxx test Trigger and Switch Boxes

[jerms01]

0G74xxxx
https://www.youtube.com/watch?time_c...&v=PVrk42hoDO8


Hey guys I have been having a problem for the last couple of months. Really rough idle if it will idle at all and a loss of Hp/top end (about 9mph).


I have already done the following and would like help in testing the Trigger and Switch Boxes while in the garrage if possible. I only have a digital multimeter please let me know if this will suffice or will I need analog?


Cleaned the VST, screen, and Fuel Pump
Replaced Fuel Lines
Tested Compression on Cylinders
Verified Spark on all 6 plugs
Replaced Plugs
Replaced Filter/Seperator
Verified I am getting 36psi from fuel pressure regulator.
Also planning on sending in the fuel rail and injectors for cleaning.


I think I need to replace my tach as the RPMs are jumping all over the place. While off its sits at 1000. I do have a Service Tach I can use for testing.


Any help here would be greatly appreciated.


TIA
Jeremy

[JOE54]

have sensors tested air and cyl head temp bad one will kill it

[jerms01]

Air Temperature Sensor & Engine Head Temperature Sensor? Can I test these or do I need to take them in?

[JOE54]

ya could may need serv manual though,check pulse pump too

[jerms01]

Is it true that when testing spark/voltage across coils or plugs (anything that is rapid pulse) that I need an analog multi-meter? I've heard the pulse happens too fast for a digital to properly capture and report.
As for the pulse fuel pump the VST seems to stay full and the primer bulb stays tight, would you assume that its working at that point?

[JOE54]

personally I have always used analog when testing volt but wouldn't think it matter with dva adapt,pulse oump can leak into crankcase causing rich condition don't bypass this overlooked part of the diagnosis have seen many cured by this simple repair hope this helps ya joe

[jerms01]

Ok will do I am looking at the repair manual now on how to rebuild. Thank you for your help sir!

[bnt55]

Air Temperature Sensor & Engine Head Temperature Sensor? Can I test these or do I need to take them in?

It is detailed in manual and is relatively simple. Take each sensor out of motor and put into ice water, the take an Ohm reading between the wire leads on each sensor while in the cold water. You will see the Ohm meter value changing as the sensor gets colder, that is a sign of a healthy temp sensor.

[jerms01]

Awesome thank you sir I will check that when I get home.

[jerms01]

Well both sensors tested and showed drops and rises in resistance as expected. Gonna check all the coils and switch boxes today when the neighbors wake up. How can I test the pulse pump to see if it's leaking into the case?

[jerms01]

Gap tested the spark from coils and had a strong blue for each one. Would that eliminate spark as the problem other than maybe timing?

[jerms01]

Well I rebuilt the pulse pump last night and it seemed to fire right up and sounded great. Throttle response seemed better as well. I am taking it out for a test run tomorrow. Keep your fingers crossed for me I've got high hopes! Thanks for all your input fellas!

[jerms01]

Well it definitely ran better but still not quite right. Gonna pressure test all the cylinders tonight only tested 2 the first time. If those all look good then I am taking it in. Too impatient and need my boat back to normal. I tried and learned a ton but time to get it to the pros.

[jerms01]

Well turns out it was 2 broken reeds on #1 and 2. Will be ready to roll next week!