No start - Cranks for 3 seconds then stops cranking

[RussMcB]

I did a bit of searching, and haven't heard of this particular symptom, so I thought I'd post here.

Symptom: Car cranks strongly for exactly 3 seconds, then abruptly stops cranking. It is very repeatable. It's done this about 12 times in a row now.

I've just reinstalled the plenum, so the problem is very likely something I did wrong while putting it together. Tonight I'll probably take it back off to look for the problem, but thought I'd go ahead and post here to get any thoughts.

A guess: It seems like the starter is cranking well, and then the ECU doesn't get a signal it expects, so it shuts down.

I had the plenum off to troubleshoot a big vacuum leak. Before I put it back on I made two changes (both related to vacuum lines):

1) I removed the larger, evap hard lines. I left the solenoid plugged in. I plugged the port under the plenum, but left the hose going to the back of the car unplugged.

2) I removed the smaller hard lines from under the plenum and routed new rubber lines from a plenum side port, through the check valve and then to the HVAC and cruise control.

I don't think my no-start is due to the vacuum line changes, but could be wrong.

When installing the plenum I was pretty careful with electrical plugs and all, but could have screwed something up.

Thanks.

PS. According to my aftermarket gauge, I have good fuel pressure. I do not have any codes. I have not checked a plug wire for spark yet. Battery has a full charge. I forgot to look at the tach to see if it showed RPMs during cranking. I do have (what I believe are the normal) lights on in the dash and information center screens.

[We Gone]

My best guess would be that one of the plugs on the electronics under the plenum is not seated all the way or a bent pin.

[RussMcB]

Originally Posted by We Gone

My best guess would be that one of the plugs on the electronics under the plenum is not seated all the way or a bent pin.

Good guess, Steve.

The problem was (this is really embarrassing) I had not attached either of the two plugs going to the module mounted in the center, underneath the plenum.

I feel stupid, but relieved that it was an easy fix. And maybe someone in the future will have this same symptom and be able to know the cause quickly.

Thanks for the replies, and thanks to Marc H for taking my call today, He had some good thoughts that helped me eliminate some possible causes.

[Gunny]

Originally Posted by RussMcB

.... I had not attached either of the two plugs going to the module mounted in the center, underneath the plenum ....

wish I could say (with a straight face, of course) that has never happened to me

[Paul Workman]

I agree w/ U Gunny... That "loose nut behind the steering wheel" gets me every time!!!