Gentlemen

Please let me start by saying I have been following this board for some time now and all of you have been very helpful, this is the first time I have found the need to post myself, but I dont know what the h*ll is wrong.

I have a 87 iroc that I just recently put a motor and tranny in, I had it running, but it lacked power, I finally decided to recheck the plug wires and sure enough there were 2 wrong, I changed them started the car, it ran for about 15 seconds (sounded much better) then died, it will now not start at all, the computer will not go into diag mode (by putting the jumpers in the computer interface) the check engine light does not light when trying to start it, everything else works lights windows the engine turns over but that is it.

the engine is a rebuilt 350 tpi that ran great in the 85 iroc I pulled it out of.

I also had to relocate the oil pressure sender for the fuel pump to the top of the motor if this switch has failed would that prevent it from starting ?

Is my computer fried ?

what should I be checking ?

thanks to anyone who replies

 

an 85 Iroc 350 TPI?

They didn't have them in 85, maybe thats the problem?

Yes if your fuel pump relay fails the engine wont start, when you turn the key on (but dont crank) do you hear the fuel pump prime?

 

ah humor I love it !

yes you are correct 305 was stock in the 85 Iroc I remove engine from, however it was replaced with a remanufactured 350
before I purchased.

No I do not hear the fuel pump run when I turn ignition on. !


Would that oil pressure switch for the fuel pump disable the computer as well ?


thanks again

 

No nothing *disables* the computer, at least hopefully.


But if your fuel pump relay is bad... and your fuel pump doesn't prime, then thats why it isn't running. It should prime when you turn your key to accessory.

 

Ok so your saying I might want to check or replace the fuel pump relay, and or the backup relay (didnt know there was a "backup relay"

Would the relay work from my 85 then ? just to see if that is the problem

I will check that when I go home for lunch today !

Any clue why the computer wont go into Diag mode then ?

after it wouldnt run I tried to see if I could get a code to show up
but it would not.

thanks for the help Tpi_roc

 

I dont know what to say about diag mode other than maybe some wiring problems?


Im using my 85 fuel pump relay for my 165 ecm, and will be using it for the 730 ecm, so yea it should work just fine.

sorry about that backup thing I got myself confused on somethin else

 

If you want to check if your ecm is good. Pull it out from under the dash and remove the chip. Then turn the key to the on position. The fans should come on automatically. If they do not it is a good sign your ecm has hit the skids. If they do come back and we will try something else.

 

Thanks for the suggestions guy's

I will change fuel pump relay, and pull chip from ecm and look for fan operation.

I will be back with an update after lunch

 

Well looks like it sucks to be me !

I went home at lunch, changed out fuel pump relay, that did not help, still does not start, and the fuel pump does not prime the system.

I also pulled the computer down from the dash, and removed the chip, turned on the ignition,,,,the fan(s) did not come on.

if the ECM is bad, is that just the chip or the whole computer ?



looks like I need options for obtaining a new computer more than likely ?

any more suggestions would be more than welcome

 

Whole computer....


Did you pull the memcal? Or the prom from the memcal?

 

I pulled the chip (wide chip with the little tabs on both sides) out of the main computer box, and left the box plugged in.

 

I *might* be wrong here, but the memcal (less prom) controlls limp home mode (When your fans stay running) so pulling the entire memcal might not do that...


Let me go try it on my car and see what happens

 

I had to remove a metal plate to get at it secured with 2 screws

 

It sound s like you need a new ECM IF you go to autozone.com you can price one. They are about 60 dollars if you return your core. I have worked on many of these and every time I pull the memcal out of the ECM or I do not get it seated right they usually go into limp home mode.

 

So the memcal is the "chip" I pulled out, and the ECM is the main box correct ?

Can you give me a guess as to why the ECM would have fried (if it is) , like I said before it was running, I shut it off and changed 2 plug wires around then restarted, it ran for maybe 15 seconds then died. ?

Nice to hear the ECM can be replaced fairly cheaply, will I be able to use the "chip" I have now or will that need to be replaced as well ?
(might be a good time to upgrade to a performance chip I guess)

thank you

 

The memcal is the plastic molded piece that snaps into the ecm, on the memcal (under the usually blue cover) is like 3 proms, the main prom which stores most of the data, then 2 other little proms for knock filtering and I *thought* the limp home calibrations. People who burn custom proms actually disassemble the memcal and pull that prom off, replacing it with the newly burnt ones



I bought a speed density computer for $30

so yea its cheap, but they dont go out usually for no good reason, you'd have to have shorted something

 

Well looks like I am on a mission then !

I will purchase a new ECM, and check all wiring looking for a short
before installation.

unless anyone has any further suggestions, I would like to thank both of you for your assistance as it was much appreciated.

Happy Day !

 

Im hardly the smartest 'tech' here but Im curious if you checked your fuses?

As I recall, the fuel pump has a fuse in your underdash fuse panel, and if it blew, it could be causing the problem. When you replaced the relay, did you test the positive wire on the fuel pump relay itself with the car turned to acc/on?

Also, my car ran screwy for a while, and wouldn't throw me ANY codes either, my problem ended up being a bad ECM too, and a replacement totally fixed my problem. My car did start and run though, even witht he bad ecm, and I could hear my fuel pump whine when I turned my key.

Hope I helped some!

 

How hot was it out? I have found extreme heat can take these ECMs out. Do you have speed density or mass airflow? You will need to keep your memcal(the blue thing) and the metal lid when you go to buy a new ECM. If you did somehow possibly mess something up, I would start looking at the distributor. After studying the schematic for both the 165 and 730 ecms it looks as if the white EST wire coming from the distributor has the ability to smoke the ECM if it sees any large amounts of voltage. It is looking for a frequency. This wire goes into the distrubutor, to the ignition module, and then to the pickup coil. Next check your black and tan wire that is to be disconnected to set the timing.

Good luck tell us how it goes

 

it was worth askin, but I did check all the fuses under dash, they all tested good with a meter.

I did not test the positive lead on fuel pump relay, I will figure out which is the + and test after work.



yes it seems as though I might have 2 problems
ECM, and the fuel pump/fuel pump curcuit

the more info the better thank you

 

Why are you worried about the fuel pump circuit? The computer runs this for two seconds when it is first powered up. If it is not happening that is another sign the ecm has seen its last days in an f-body

 

it was bout 80 outside yesterday when I was working on it.

It is a MAF system

The distributor info will be real useful , thank you

I will provide update

thanks again everyone !!

 

Davecs1

Good point, first the ECM swap and go from there !

thank you