setting time on a 5.7

[scottberry]

I have a mid 90's 5.7 mercruiser with a TBI. I set the time in the driveway with timing light to 8 degrees advance. Seemed to run fine. Put it in the water and no power. Raised the cover and adjusted the distributer while under load and the speed picked up. I just left it alone for the day. Next time out, I had some power loss and a little back fire through the TBI under heavy load (more weight and getting out of the hole). After a few minutes it finally regains power but not perfect. A little stuterring at low RPM's. I am sure the timing is off a little. When I got back home, I put the timing light on it again and it looks way advanced. The mark isn't even close to the timing tab.

Is there a trick to setting the time in the yard versus in the water? Do I need a reader of some sort rather than the traditional timing light?

 

[Don S]

Re: setting time on a 5.7

Did you put it in service mode/base timing mode before you set the timing?

 

[scottberry]

Re: setting time on a 5.7

I guess not. How do I do that without any special tools or diagnostic devices.

 

[scottberry]

Re: setting time on a 5.7

From what I have been reading there is a purple/white wire somewhere around the distributor that needs to be connected to ground to put the ecm in service mode. I don't see this wire just by looking. It could be hidden somewhere since the motor has been changed a couple of times. Can anyone tell me where th e purlp/white wire originates from so I can trace it down?

Thanks.

 

[rfelectron]

Re: setting time on a 5.7

I have a '94 5.7L TBI with the GM EST ignition. My engine has a 10 pin diagnostic link just like a GM car. The diagnostic link is located in the vicinity of the ECM. Make a jumper out of a paper clip and short pins A and B together to put it in service mode. Then bring the rpm's up to 1200 or so so the engine is running smoothly and the timing mark isn't jumping around. Set the base timing to 8 deg BTDC. Tighten down the dist clamp, unplug the paper clip and you're done.

 

[Zackman]

Re: setting time on a 5.7

Here's what the manual states:

EFI / MPI Models
1. Connect timing light to number 1 spark plug wire.
2. Start engine and run at 1300 rpm until it reaches normal operating temperature.
3. Stop engine and connect the scan tool or timing tool to the DLC connector on the EFI/MPI wiring harness.
4. Start engine, allow rpm to stabilize.

NOTE:
MEFI-1 models only, manually adjust remote control throttle lever to get 1200 engine rpm.

NOTE:
MEFI-2 and MEFI-3 models only, ECM will automatically adjust engine rpm to
approximately 1200 rpm when put in the service mode on a scan tool or when using the timing tool.

5. Check ignition timing. If incorrect, rotate the distributor until timing is correct. Torque clamping screw to 18 lb-ft (25 Nm).
6. Recheck ignition timing.
7. Disconnect scan tool or timing tool from DLC connector.
8. If required, return remote control throttle lever to idle position and shut off engine.
9. Restart engine, increase rpm to 1300 then return to idle position slowly. Ensure that
engine returns to idle rpm. Readjust throttle cable, if required.

10. Shut engine off.​

 

[TilliamWe]

Re: setting time on a 5.7

Hope this helps