85 start issue

[bluemane500]

hey guys i have an 85 that is having a problem,if you turn the key it will crank but not start,,, so while checking the power at the fuse box to the fuel pump i noticed with a slight tap of the key it starts,,, so i changed the ignition switch figuring that was the culprit but it is doing the same thing,, any suggestions thanx in advance

[Capt J.D.]

Most probably either the reference sender or speed sensor.

[Icemaster]

With a slight tap of the key, the engine starts or the fuel pump starts? Or did changing the ignition switch stop the slight tap issue?

My first stop is always the DME relay. Under the front seat.

[bluemane500]

with a slight tap of the key the engine starts ,

[bluemane500]

and when i changed the ignition switch the problem remained the same

[Icemaster]

If it starts, it's not the DME.

[Flat Six]

Based on what you've described I'd bet it's the FP relay. Could be intermittent DME relay (I guess maybe they're all intermittent?) so I'd try R&R of that first. But also R&R FP relay -- loose/dirty connection or intermittent/failing relay. Cheap replacement.

Hope this helps.

Dale

[kidrock]

turning the fuses and changing the relays are easy and quick. But you really need to isolate the issue and find out whether you are lacking fuel or spark. Next time the car refuses to start, do a fuel and spark check.