mercruiser 7.4 mpi cold start stalling

[jmowood]

fuel pressure ignition on engine off hits 45 for 2 seconds then dropps to 38, again not running the engine??

 

[alldodge]

Looks like I missed part of the testing, the 4V is a bit high so try this part

 

[jmowood]

so i am confused? is 3.6 and 3.7 volts ok?
and post 22 where is step 1, 2, 3 4
am i just checking the sensor itself? if so do i remove it from the engine or leave it in? ignition on or off?

 

[jmowood]

my J2 -11 is 410 yellow and J2-18 is 814 black. seems to be different from post #15 not sure what ohms setting i should be in?

 

[alldodge]

Have to apologize, here I thought I posted all the pages then see I didn't. My only flimsy excuse is doing to many things at once.
Here is the first part of checking the connections and resistance values at the sensor. You shouldn't need to remove the sensor to test. Now you should be getting 4V but this could be just because of your meter, may not be accurate or something else. If after everything is checked out and voltage is still low then we may need to think about the ECM.

I see the wires should be yellow and black, think your good. Checking the sensor should be on the ohms scale, and if your around 32 degrees then you should read between 7500 and 13500 ohms

 

[jmowood]

Step 7 says to disconnect J1. Am I disconnecting J2 that's where my ECT is harnessed.

 

[alldodge]

Are you sure your on J2 ?

 

[jmowood]

yes j2 has the yellow wire in it

i just rechecked the circuit ECT now getting 4.7 volts on 2 different meter

 

[alldodge]

yes j2 has the yellow wire in it

i just rechecked the circuit ECT now getting 4.7 volts on 2 different meter

The voltage sounds good, so your ECM is checking out. Only thing I can figure is the manual I'm looking at has a later revision.

How did the resistance on the sensor check out, with no wires connected?

 

[jmowood]

i cant really get to it with out removing it? should i remove it?

 

[alldodge]

You can remove it, but then your antifreeze will come pouring out. Since you can get to the ECM connector go from the pins to the sender to see if you get readings close to what you should see

 

[jmowood]

no antifreeze. seawater cooled

 

[alldodge]

OK then just pull it out. Remember when reinstalling, no more then 2 1/2 turns once hand tight

 

[jmowood]

engine is slightly warm and im getting 1800-1900 ohms

 

[alldodge]

Put it in the freezer and check. Then check a couple more times as it starts to get warmer. If you can get it close to zero then as it warms up see what happens. Need to see if it goes above 25K ohms as it gets cold

 

[jmowood]

removed the sensor and i cant get a reading. does holding it in my hand affect the resistance? there are several settings on the meter. not sure which one to set it on

 

[jmowood]

getting 9.5 ohns when on ice. assuming its 9500

 

[alldodge]

getting 9.5 ohns when on ice. assuming its 9500

The meter should show a K or M along with the numbers. So 9.5 K then 9500 or M for 9500000. If it is at 32 degrees and your getting 9500 ohms or 9.5 ohms that's bad. It should read 24K (24000) ohms or more. Now if it's 9.5 M then you should be good, maybe

Edit: take the 9.5M back, that would be way to high

 

[jmowood]

ok here is the scoup. after having trouble with the ohms meter i replaced the ECT with a new one . the voltage is 4.8 at the ECT harness. runs great after warm. tomorrow morning will be the real test to see if she stalls. fuel pressure starts out an 45 psi during the first 2 seconds of ignition on engine off. then drops to 38..then once she starts up is stays around 38psi while running. so wonder if thats normal.

 

[alldodge]

I hope that fixes it, look forward to the morning start.

Manual shows 43psi running, I take it as idle, but could also be at high idle. Would also say that 38 isn't to far off, and should run even cold. Main issue I would see with a bit low pressure would be running lean at higher rpms.