7.4L MPI Timing Issue
02-21-2006 | 08:53 AM
#1
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From: Lake Champlain
7.4L MPI Timing Issue
First post, woohoo! 
I have a '99 7.4L MPI, during spring maintenance I changed cap and rotor and of course misplaced a few plug wires. I cheated for #1 TDC by removing every plug but #1 and cranked by hand until I could barely move the crank any further. I get the timing mark to ~8 BTDC and pulled the rotor to see where #1 post was. Started installing wires one at a time from there in firing order. I still cannot get the motor to start.
One major thing I noticed is that I have some play in the rotor, not much but it also moves up and down a little. When moving the rotor like this the ECM seems to kick on and off triggering the fuel pump to do its 5 second pressure build. I can sit there and wiggle the rotor and it will just keep doing it. Any idea what could cause this slack to trigger the ECM to do anything at all? The engine has ~300 hours and I suppose it's possible to have some cam gear or distributor gear wear but why would this cause any relays or sensors on the motor to do anything?
I have a '99 7.4L MPI, during spring maintenance I changed cap and rotor and of course misplaced a few plug wires. I cheated for #1 TDC by removing every plug but #1 and cranked by hand until I could barely move the crank any further. I get the timing mark to ~8 BTDC and pulled the rotor to see where #1 post was. Started installing wires one at a time from there in firing order. I still cannot get the motor to start.
One major thing I noticed is that I have some play in the rotor, not much but it also moves up and down a little. When moving the rotor like this the ECM seems to kick on and off triggering the fuel pump to do its 5 second pressure build. I can sit there and wiggle the rotor and it will just keep doing it. Any idea what could cause this slack to trigger the ECM to do anything at all? The engine has ~300 hours and I suppose it's possible to have some cam gear or distributor gear wear but why would this cause any relays or sensors on the motor to do anything?
02-21-2006 | 09:53 AM
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From: Newport Beach,CA
Re: 7.4L MPI Timing Issue
Is the key in the "on" position when you are moving the rotor? The ECM will turn on the fuel pump if it receives a reference signal from the ignition module, maybe you are moving the rotor just enough to create a signal. But the key would have to be on while you were doing it, and I wouldn't worry about it.
If you were cranking the engine with the wrong firing order, you may have flooded it. If you are confident that you now have the firing order correct, try to start it using "Clear Flood" mode. That is with the throttle handle moved forward to 50% to 75% open.
Dave
If you were cranking the engine with the wrong firing order, you may have flooded it. If you are confident that you now have the firing order correct, try to start it using "Clear Flood" mode. That is with the throttle handle moved forward to 50% to 75% open.
Dave
02-21-2006 | 10:02 AM
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From: Lake Champlain
Re: 7.4L MPI Timing Issue
Thanks Dave,
Yes, the key was in the ON position when this was happening. The rotor only moves a degree or 2 and maybe an 1/8" up and down, not very much slack but the fact that the ECM was telling the system to do things had me slightly concerned.
I think I am going to pull the distributor (I snapped a cap screw off anyways) and the valve covers to get the motor to exactly TDC and reset the base timing. Also a perfect time to install the MSD 8.5mm wires I picked up.
Yes, the key was in the ON position when this was happening. The rotor only moves a degree or 2 and maybe an 1/8" up and down, not very much slack but the fact that the ECM was telling the system to do things had me slightly concerned.
I think I am going to pull the distributor (I snapped a cap screw off anyways) and the valve covers to get the motor to exactly TDC and reset the base timing. Also a perfect time to install the MSD 8.5mm wires I picked up.
