87 engine quits

[87wishin59]

Hi All,
My 87 didn't come out of storage very well this year. I need some help.

When I turn on the ignition, the cooling fan immediately starts running. The car will NOT start until the fan stops. Once it stops, the car starts right up. It may run for 5 minutes or all day, then just stops.

I wanted a fresh set of codes, so I disconnected the battery and tried again. I was getting codes 34, 51 & 46.

I had the 34 before this problem started, so I replaced the burnoff and power relays and the 34 code went away. (I checked the MAF with a DVM and it is working)

The constantly running fan kiled the battery. It was about time for a new one anyway so I replaced the battery.

I still have the problem where the primary cooling fan comes on as soon as the ignition is turned on, car will not start while the fan is running (engine turns over, catches for an instant then stops) fan runs for about 2 minutes, stops, car will start. Sit there and idle, then just stop. No codes.

Hard to believe the PROM is bad, hate to just throw a new ECM at it.

All ideas welcome!
Thanks in advance,
wojo

 

[vets4-2]

code 51 Is a prom error code 46 is a vats code

 

[Harry1987]

Sounds Like Temp Sensor

Your primary fan shouldn't come on until your engine temp exceeds a certain level (180 degrees I think). The ECM monitors engine temp and sends the relay control return signal and the fan power actually comes directly from your battery to the fan relay. Your fan will also come on automatically when in diagnostic mode. Check your computer port under your dash, drivers side to the right . If upper right two pins are shorted together you will be in diagnostic mode and your check engine light will blink 12 and them some other codes will follow.

If all seems OK, check your fan relay connections(primary on drivers side inner wheel well) and secondary drivers side near radiator.

Good Luck!

 

[87wishin59]

Hi all again,
Well, the vette is still broken. I thought I'd check one last time before I have it towed to the dealer.

The symptom is still the same, when I turn on the car, the primary radiator fan immediately comes on, the car will not start until the fan stops. While it was doing this, I just sat there and let it run. Lo and behold, the service engine light starts blinking a "12" - the car thinks it's in diagnostic mode! That certainly explains the fan running. Nope, I don't have the aldl pins jumpered. The other interesting thing is that the avg MPG display will read "12.8" when the car *Won't * start and "0.0" when the car will start. Every once in a while the car will start but idle rough. I've changed the PROM, since I was getting a 51 code when all this began, but that didn't fix it.
Other than the ECM, is there any sensor anywhere in the car, that could fail and make the ECM believe it's in diag mode ?
Or I wonder if I don't have a bad ground somewhere - is there a typical ground fault found in the vette somewhere? (this is my fisrt vette)
Thanks again in advance,
Wojo.

 

[Harry1987]

Recheck your ALDL port

I don't have my Haynes manual here at work but when you short the two pins (If my memory serves me right its pins A and B)together your routing a ground back to the ECM. So basically one pin provides the ground and the other routes the ground back to the ECM. The routing wire may be shorting anywhere between the ALDL and the ECM. Get an ohmmeter and ohm between pins A and B of the ALDL port to see if they are shorted together. If they are I would then take a real good look at the back of the ALDL. The pins may be shorting from behind the connector. Usually they crimp a pin to the end of the wire and press it into the port housing. If one or more of the pins are not fully inserted they could be shorting together.
Take a good look at where the ALDL wire connects to the ECM. The pin may be crimped there. If your not careful inserting the ECM back under the dash you can easily crimp a wire there. As a matter of fact I would pull the ECM from under the dash without disconnecting it and see if the problem is gone. Wprse case I would cut the wire check for the short if its still there run a new wire form the ALDL to the ECM

 

[Eagle85C4]

This is an extremely long shot...but by any chance could a mouse have gotten under the dash during storage? I have seen this happen as they like the insulation for making a home and love to chew the insulation off the wires...remove the center console and do a good look...you may be surprised. And boy is this a long shot.....

 

[87wishin59]

Thanks Harry and Eagle for the advice.

Well, my wife never ran screaming from the garage, so I'm guessing there was no mouse, (I stored the car at home; garage is attached) but hey, thanks for the thought!

A check at the aldl (or is it asdl?) pins A&B with a meter shows 10.32k ohms and 5.02 v with the ignition on. The car started twice during my tinkering, sat there and idled for several minutes just fine once, died after a minute the second time. 2 hours later though, I couldn't even get the ECM into diag mode with A&B jumpered, fan just ran forever, several times I could hear the fan relay having a fit (clicking off and on rapidly), the Service light would blink during those times too. I'd turn off the igniotion just to make sure I didn't break anything else. When it does start, it seems fine and there are still no codes in the ECM which is why I'm shy about replacing the non-returnable ECM and I don't have the guts to try a $227 Delco ECM and be wrong (or a good divorce lawyer ;-), so I guess it's the big hook for my baby and a trip to the dealer
Man, I Hate to lose to a machine....

 

[Harry1987]

Wife does Need to know the details

If my wife knew the money I put into my Vette she'd flip. There's some things she doesn't need to know. An ECM from an auto part store should probably cost about $150 with core and its a fast change. If it doesn't fix it you can get some of your money back selling it here. Don't give up on your Vette unless you're going to the dealer to buy another

Good Luck,
Harry