dnwong

I tried to start the car this morning. Car kept cranking. I looked at the tach and the tach jumped to 3000 for second and then back down and started bouncing around 0.

Any thoughts?

jpk

I'm chasing down the same problem in my '84. When I checked the resistance of the ref & speed sensors, the ref sensor checked out OK, but the speed sensor didn't. I thought that was my problem. The condition of the wires to it were also really sketchey, so I ordered a new one and replaced it. It didn't help.

I've checked and rulled out a number of other things - AFM, TPS, good spark, etc...

I can actually get the car to run if I hold the throttle wide open while cranking. It will run very rough though - as if the ignition timing was way off (if and when I get the rpm's to build to around 4k, it sounds much better - almost normal)

I'm almost convinced the problem is in the DME itself.

skene

If the tach is bouncing, then it's not the ref. sensors. When they don't work right the tach doesn't move at all. A bad DME relay or cold solder joints in the DME are pretty common faults as well. I've got a spare DME relay you can borrow for a bit if you want to test that.

jpk, you might want to check the female connection of the sensors. Mine were all cracked and shorting out. I soldered on new connectors to the harnes side and haven't seen my no-starting issue since. You can get parts at www.kayjayco.com or www.eagleday.com and I think Lindsey racing now sells a kit for them.
Another thing to check is the TPS, since you said holding the throttle open works sometimes?

2BWise

FPR?

dnwong

The reason I think its the ref sensor is that when the car came back from the clutch job last week, it was having problems starting. The starter would choke while trying to crank the car, hesitate and crank then hesitate again before the car actually started.

I thought the problem was the starter, so I was at advanced auto to buy a new starter when all of the sudden the problem went away. Drove all day yesterday. This morning the car cranks fine (like the obstruction went away), but the tach is all over the place. So, I am thinking the sensor got wacked or knocked out of the way.

Dudley

dnwong

What is a FBR?

2BWise

fuel pressure regulator

xsboost90

the ref sensors wouldnt make the starter stop/start. If the ref sensors were bad it would crank crank and not start- no fuel/spark. If its hesitating I would check your wires on the battery and starter, as well as the ground on the bellhousing if you just had all that apart. IF any are loose it may do this.

Rock

If the tach is jumping to 3k then i think youve got a bad ground.

I went crazy tracing a no start problem on my black car. The tach would jump to 3k and not start, and it would do funny stuff like if I honked the horn, the tach would rise. The starter would also work intermittedly. It ended up being a loose ground by the battery. Id check your grounds.

skene

Rock might be onto something there too. The grounds are next to the ref. sensors in the back, so it's possible they's a loose connection there after doing the clutch work. I was wrong about the 3k thing before btw, my car jumps up to around 1k at the most. Sorry, wasn't thinking right.

Rock

Well there is a ground right behind the sensors at the back of the engine

the must likely culprit would be the ground thats on the bellhousing seeing as how it was probally messed with to change the clutch.

dnwong

Well, the shop who did the clutch offered to have it towed back and they would diagnose. Told them about the ground issue. We will see what happens.

MM951

They probably did what I did and stressed the already weak wire connection at the speed/ref sensors (they have to come out to do a clutch) They are fine to move around when new/not brittle but when the wire is exposed or they get old and brittle gooood bye running car

Did your tach jump around then the car start cutting out..then die?

dnwong

I don't remember how the tach was acting when the starter was struggling. But now the starter works fine and the ref sensor still having problems.

dnwong

Took car to shop and then all of the sudden it would start again. So, took it home and ran it for the last few days.

This morning the car would not start again...

The car would run fine for many days and then all of the sudden, one morning it would not start. It just keeps cranking and cranking. Checked and ohmed the sensors, tapped the DME and jumped the DME relay. Still no start.

I unhooked the speed sensor and left the ref sensor hooked up. Then checked the tach while cranking. Should there be any tach movement or is the movement only for the speed sensor? I got no movement. However, when I put the speed sensor back on, the tach is doing that funny thing again. Jumps to 3000 and settles back down while cranking.

Any ideas?