Crank but no start. Conection to Fuel pump. Bad ECU.

[dietztho000]

I have a 93 SHO. ATX. It wouldnt start so we tweeked with everthing to find out why.
Also my check engine light came on and showed the code "511 - Read only memory test failed - replace ECA"

In the process of figuring out why the car didnt start, it was because the fuel pump wasn't receiving any power. So we took speaker wire from the battery to the fuel pump power wire and started the car fine. It would then beable to start up a couple more times before it would just crank again. So we came to the conclusion that it was the ECU.
My ECU came in yesterday and I put it in today.
After I put it in, I started the car once, and it started right up! I then shut it off and tried it again to move the car so i can finally wash it, but this time, it doesn't start. and now it still doesn't start. The fuel pump does sound like it goes on though. but im not 100% sure of this.

I'm very frusterated about this. I figured it would be the computer, and it did fix it, to run once...and now it just happens again.

Any ideas what could be stopping it from starting?

BTW it was a used computer i got, but i doubt I'd be unlucky enough to pick up another corrupt ECU. but maybe.

 

[hawkeye18]

ECUs on the SHO very rarely go bad; the odds of you having had one bad ECU, let alone two, are near astronomical.

Did you check the first ECU for anything dangling of the connector on the cabin side of the computer? Any aftermarket chip will cause a 511 error.

The fact that it started at all with the old ECU tells me it wasn't bad.

You should focus your attentions on a) the fuel pump itself (as they do go intermittently bad), and b) the IRCM (or ICRM or whatever the acronym)... it's the relay box mounted on the radiator support on the driver's side. It'll have a big "J" on it.

That box controls the relays that take the fuel pump "turn on" signal, and actually turn the fuel pump on. The relays route battery power to where it is needed. If the fuel pump relay is bad or sticking, that will cause the symptoms you are describing.

One solution for sticky relays is to have a "conversation" with them. This involves disconnecting it (mind the 8mm bolt in the middle of the connector), finding a nice flat hard non-scratch surface (concrete works well) and banging the flat top of the box against it a few times. This jars the relays around and in many cases unsticks them. Also called an Italian Tuneup.

 

[dietztho000]

Thank you so much for the detailed response!
I actually do have a "Superchip" that was connected to the old ECU. I didn't add it onto the new ECU, but I was going to if the car started again. Im going to try what you said and Ill keep you informed!
Once again, Thank you so much!

 

[dietztho000]

Hey Hawk,
When the turn the key to the on position, the relay ticks like it is suppose to. and the fuel pump does sound like it turns on.
So I think the new computer did help, but it also made a new problem occur?
I'm unsure as where to start next. Just because the ticking is happening, could it still mean a bad relay?
And also, do you have A picture where the relay is located because my J is worn off of it. I'm thinking its the relay under the black plastic cover thing in the front right. Thats where the ticking is coming from

 

[luigisho]

Might be where you're looking up and back from the radiator. Plastic module. Shouldn't be many things clicking. -If- you have fuel, you might have a sensor problem with spark. Verify the fuel is good, verify spark is good.

 

[dietztho000]

Problem Resolved...it was the Computer Module relay that needed to be replaced. Starts up like a champ again! thanks for all the help guys.

 

[ShoNuff91]

Bump. Okay where exactly did you find the computer module relay that you replaced?

 

[luigisho]

What are you looking for? The relay control module is on upper right of the top of the radiator. Should have a big letter on it.