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-   General Q & A (https://www.offshoreonly.com/forums/general-q-20/)
-   -   7.4 mpi timing issues (https://www.offshoreonly.com/forums/general-q/359670-7-4-mpi-timing-issues.html)

troc 03-21-2019 04:51 PM
yes sir, My friend 14apache said you were the man to talk to lol

troc 03-21-2019 04:56 PM
Originally Posted by BUP (Post 4677967)
you did put the scan tool in service mode ?? for setting and checking the timing Im just checking
Yes sir I used my rinda scanner

troc 03-21-2019 05:04 PM
Originally Posted by MDG_Jason (Post 4678039)
How much timing are you getting? Some of those 7.4s did not have much timing in them from the factory
about 28 deg at 2700 then the timing starts to peel off down to 19deg as RPMs increase

F-2 Speedy 03-21-2019 05:13 PM
Is this a MEFI 3 ......is the knock sensor connected ?.......seems the ECM thinks there's a problem and is pulling timing out

AllDodge 03-21-2019 05:19 PM
with a carb and mechanical distributor and it made 315hp I suggested to put MPI and ecm on and rerun it. It would only make 275 hp
I'm thinking you need to pull the motor apart and find out what was not put together correctly. Even a carb motor with 088 heads should make more then 315hp with fresh rebuild

troc 03-21-2019 05:20 PM
Originally Posted by BUP (Post 4677967)
you did put the scan tool in service mode ?? for setting and checking the timing Im just checking
I did , scanner matched timing light on the balancer . timing starts to increase ,then just peels off as rpms increase I swapped out the knock sensor, but im wondering if i should check voltage on the ECM pertaing to knock/advance? I believe its J1-1? waiting for the manual I ordered to show up to verify I appreciate the responses!

AllDodge 03-21-2019 05:35 PM
Originally Posted by troc (Post 4678178)
I did , scanner matched timing light on the balancer . timing starts to increase ,then just peels off as rpms increase I swapped out the knock sensor, but im wondering if i should check voltage on the ECM pertaing to knock/advance? I believe its J1-1? waiting for the manual I ordered to show up to verify I appreciate the responses!
With the MEFI3 (EDIT once its running), you can just remove the knock sensor wire off the sensor and move it out of the way. If power increases, the sensor is picking up a knock and retarding timing. If it does increase power after wire is removed "SHUT IT DOWN" because your destroying the motor

troc 03-21-2019 06:05 PM
Originally Posted by F-2 Speedy (Post 4678176)
Is this a MEFI 3 ......is the knock sensor connected ?.......seems the ECM thinks there's a problem and is pulling timing out
I think im going to find the ECM input that controlls knock next. TWO ecms doing the very same thing...starting to run out of ideas lol

troc 03-21-2019 06:09 PM
Originally Posted by AllDodge (Post 4678181)
With the MEFI3 (EDIT once its running), you can just remove the knock sensor wire off the sensor and move it out of the way. If power increases, the sensor is picking up a knock and retarding timing. If it does increase power after wire is removed "SHUT IT DOWN" because your destroying the motor
agreed , ran some good fuel on the dyno and did exactly that...even with sensor wire disconnected the knock module is still in the circuit, no?

F-2 Speedy 03-21-2019 06:18 PM
Id pull the front cover and check the timing marks, pull the distributor, remark #1 and restab the dist .............I dont think its an ECM issue, the engine isn't happy


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