85 wont start - help

[Bigbartguy]

Talk about frustrating. Car drove perfect all day. Went to leave for the evening and the simply wont start. Turns over and sounds like it wants to, but just wont. I disconnected the Cylinder Head Temp sensor (which will supposedly make it run rich by disconnecting) and I am able to get it to start & run, although very poorly.

I replaced the CHT sensor & swapped out the DME relay- problem still exists.

In the last 6 mos I've replaced: O2 sensor, DME relay, Dist cap, rotor, plugs. Also had the air/fuel mixture adjusted to specs and valve adjustment done.

Idle speed valve appears to be working fine.

Does anyone have an idea about what my prob could be? I live in MN and I only have about 4 weeks left of enjoying the car before tundra sets in.

please help and thank you!

[marcesq]

Tim:

Did you try disconnecting the O2 sensor after the CHT sensor was unplugged?? New dosen't mean it still works, plus it is a simple thing to rule out.

Try the O2 sensor and repost.

Thanks

[stlrj]

I wonder if your fuel pump went out. Too bad there wasn't an easy was to check for fuel pressure.

Cheers,

Joe

[marcesq]

Test the fuel pump by running a wire from the top of fuse 6 to bottom of fuse 3 (counting only the middle block of fuses and not from the front or rear of the panel). The #1 fuse of the middle block is closest to the master cyl.

Oh yea turn the key to the on position.

If you do not hear a strong constant whirring noise then it could be the pump.

[ChrisBennet]

The O2 sensor is ignored during starting.
It test the fuel pump by running a jumper (momentarily) between bottom of fuel pump fuse and the the bottom of an adjacent fuse and listen for whine of fuel pump. By using adjacent fuses you can use anything (screw driver, etc) for a jumper.
If you have an oscilloscope, check the speed and reference sensors. If they haven't been replaced ever it wouldn't hurt to replace them anyway. The heat kills the wires for these sensors. Try wiggling the sensor wires and then starting.
-Chris

[Bigbartguy]

The fuel pump whirs and tests ok. I jiggled the sensor wires and no change. I tested the air flow sensor and meter, and the vane moves freely and the electric stuff is within Bentley specs. Also tested the Intake Air Temp (ATF) sensor and it's ok. The idle position switch is w/i specs also.

Because it will start with the CHT disconnected (which, when disconnected is suppose to cause the motor to run rich) I'm inclined to think my ignition system is ok. It sounds like a mixture issue ?? I'm pretty lost at this point.

Additionally, my tach has been intermittently going crazy. Occassionally the tach will almost act in reverse (idles at 6000 rpm). This has now became a f/t issue.....turn on the key, the tach shoots right to 7000 rpm....although the motor still ran fine when this happened. I'm not sure if the tach and start probs are related?

[scottb]

There was a thread posted recently on tach problems being the result of alternators about to go bad. You might check it out to see if it gives you any leads.

Good luck.

[RazorRacer]

Once I put my distributor cap on and it didn't sit right. The car cranked, but didn't start. I twisted the cap a bit and it clicked into postion and started right up.

Good luck, especially with only 4 weeks to go.

[R22tech]

Sounds like an alternator problem. Check archives under "alternator".

[Bigbartguy]

ok - problem solved. I feel like a complete idiot (where is that 'bonehead' post when you need it).

My gas gauge was stuck at 1/4 tank. The TANK was empty !!!! I saw it was getting spark and figured it must be a fuel issue. Then I started thinking that I havent used much gas lately.....and that got me thinking about things. Stuck a pole down the gas tank and it came up dry. Added 2 gallons, cranked it for 20 seconds and fired right up.

I guess at least my CHT got upgraded and I caught it before I towed it to the repair shop.

thanks for everyone's input.
Bigbartguy aka Bigboneheadguy

[RazorRacer]

Glad you solved the problem and it wasn't a big deal. Thanks for keeping up posted.

[scottb]

What are you going to do about the gauge?