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acefuture

It won't start - looking for a donor MEFI

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Alright well I finally got my car out of the trailer yesterday to start season prep, i know i know i know, i lagged....
Anyways, the car hasn't been started since April and has sat in the trailer since. Went to start it yesterday and put the key in the on position and the fuel pump didn't prime. Went to start it and crank crank crank, won't start, no fuel obviously. I check the fuel pump fuse, fine. Fuel pump relay, fine. Ignition fuse, fine. Power relay, fine. Everything powers up no problem. Put a hot wire from the battery straight to the fuel pump, works fine, but the car still won't start with the pump connected straight to the battery. So everything lead to the MEFI. I checked the grounds and they looked good. Checked any loose connections and lightly took the compressor to blow out all sand in the general area. Everything looks okay. So I'm assuming my MEFI took a dump over the summer. Is that a possibility? I bought it used from a guy last year who said it had been sitting on his shelf for years and he had no idea what the track record of it was. The fans don't work on the temp switch so it's kind of had issues since I bought it, but that's been it. So couple questions:

What else should I take a look at? @jjoseph99 had some good feedback and  said check the command wire for the fuel pump relay, which i'll take a look at tonight.
Any other thoughts to help diagnose?
Any one have a MEFI 4 or 4a lying around that I could borrow to plug in and see if that remedies the issue?
And if it does happen to be the computer, anyone have a MEFI 4 or 4a tuned for a stock LS1 or an LS1 with a mild cam they'd be willing to sell? Not looking for one tuned for a stroker or boost since I won't be doing either of those with this motor.

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Make sure you have your constant 12v to the ecm good and your switches 12v going to the ecm good.  

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5 minutes ago, jtmoney714 said:

Make sure you have your constant 12v to the ecm good and your switches 12v going to the ecm good.  

I had a strong 12V at my dash meter, and had 12V at everything up to the computer, after the computer I had 0V at the fuel pump, but that was the only thing I checked downstream of the computer

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I had similar issue.  Ended up being bad contact inside of plug. Can't upload pic for some reason.  But on mine was a flat 5 or 6 pin weatherpac .  Might be different for you.  

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26 minutes ago, Billyme2 said:

I had similar issue.  Ended up being bad contact inside of plug. Can't upload pic for some reason.  But on mine was a flat 5 or 6 pin weatherpac .  Might be different for you.  

What was the plug for? Was it going to or from the Mefi?

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Unfortunately I'm at work and can't upload pic. But it was on main harness. I would have to trace it out to give a good answer.  I could move it and occasionally get fuel pump to kick on. Ended up disassembling plug completely,  closing female contacts more and soldering wire into pins. Finally got good connections.  

I'll try to get you a picture when I can. 

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6 hours ago, acefuture said:

Alright well I finally got my car out of the trailer yesterday to start season prep, i know i know i know, i lagged....
Anyways, the car hasn't been started since April and has sat in the trailer since. Went to start it yesterday and put the key in the on position and the fuel pump didn't prime. Went to start it and crank crank crank, won't start, no fuel obviously. I check the fuel pump fuse, fine. Fuel pump relay, fine. Ignition fuse, fine. Power relay, fine. Everything powers up no problem. Put a hot wire from the battery straight to the fuel pump, works fine, but the car still won't start with the pump connected straight to the battery. So everything lead to the MEFI. I checked the grounds and they looked good. Checked any loose connections and lightly took the compressor to blow out all sand in the general area. Everything looks okay. So I'm assuming my MEFI took a dump over the summer. Is that a possibility? I bought it used from a guy last year who said it had been sitting on his shelf for years and he had no idea what the track record of it was. The fans don't work on the temp switch so it's kind of had issues since I bought it, but that's been it. So couple questions:

What else should I take a look at? @jjoseph99 had some good feedback and  said check the command wire for the fuel pump relay, which i'll take a look at tonight.
Any other thoughts to help diagnose?
Any one have a MEFI 4 or 4a lying around that I could borrow to plug in and see if that remedies the issue?
And if it does happen to be the computer, anyone have a MEFI 4 or 4a tuned for a stock LS1 or an LS1 with a mild cam they'd be willing to sell? Not looking for one tuned for a stroker or boost since I won't be doing either of those with this motor.

My buggy is at redline getting tuned for the turbo I added over summer. They had to switch my 4a to a 4b for the added turbo. Last tune on it was from redline for a mild cam Ls1. 

Not sure what exactly I'll get back from the upgrade but it should be back this week. You can borrow whatever I get back or we can figure something out. 🤘

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49 minutes ago, cwarkenton said:

My buggy is at redline getting tuned for the turbo I added over summer. They had to switch my 4a to a 4b for the added turbo. Last tune on it was from redline for a mild cam Ls1. 

Not sure what exactly I'll get back from the upgrade but it should be back this week. You can borrow whatever I get back or we can figure something out. 🤘

That would be epic! Let me know when you get it back. Thanks 

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Just took a look at every wire that has anything to do with the functionality of the car starting and everything is clean and connected well. Checked for voltage at all relays and everything looks good except for the wire going from the MEFI to the fuel pump relay. So at this point I’m stumped. Why would the computer not trigger it to kick on the relay? I went as far as replacing all fuses even though they looked fine and checked for continuity on the new fuses as well.

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Must be more to it. You can jump the relay if that's all it was and make fuel pressure. But you said it still won't start. 

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You checked continuity from mefi to fuel relay? 

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1 hour ago, Grease Monkey said:

Must be more to it. You can jump the relay if that's all it was and make fuel pressure. But you said it still won't start. 

Yep I did that, fuel pump working fine and supplying ample pressure but still won’t start. Just cranks and cranks. 

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1 hour ago, Billyme2 said:

You checked continuity from mefi to fuel relay? 

Power to the fuel pump from the relay is fine, but the power to the relay from the MEFI shows nothing. Grounds are fine 

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Have you checked the relay that powers the motor ? 

 

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You sure your "Ignition" wire is good?  The computer when it sees ignition will activate the pump and the ignition sequence.  If it was a fuel pump issue or relay for it you would get it to run if you jumped your fuel pump. 

Check the computer ground and ignition source.  This is probably on a relay and if its not a sealed relay it might have failed.  Change out that relay.  Had the same issue with my Holley EFI last year.  One of the wires little rubber grommet backed out so sand worked its way into the relay.  Once I put on a new relay it fired right up and ran.

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4 hours ago, chopshop said:

Have you checked the relay that powers the motor ? 

 

Yep, checked both power relay and fuel pump relay. Both are good.

 

1 hour ago, r3meyer said:

You sure your "Ignition" wire is good?  The computer when it sees ignition will activate the pump and the ignition sequence.  If it was a fuel pump issue or relay for it you would get it to run if you jumped your fuel pump. 

Check the computer ground and ignition source.  This is probably on a relay and if its not a sealed relay it might have failed.  Change out that relay.  Had the same issue with my Holley EFI last year.  One of the wires little rubber grommet backed out so sand worked its way into the relay.  Once I put on a new relay it fired right up and ran.

Yep, ignition wire is good. I have a light at the ignition that comes on when the ignition is turned to the on position. I'm seeing 12v at the fuse panel for the ignition, light is coming on, and I'm getting 12v from the ignition at the relay as well. My fans are working just fine so I took my two relays for those and put them on the power relay and fuel pump relay, no difference. 

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But....do you have ignition power AT the ECU connector?  The wire between the relay and ECU could be broken/shorted.

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1 minute ago, Kraut_n_Rice said:

But....do you have ignition power AT the ECU connector?  The wire between the relay and ECU could be broken/shorted.

I have power at the ECU from the ignition, but I do not have power at the wire from the ECU to the fuel pump relay. Which is why I'm stumped. The computer is not telling the fuel pump relay to turn on. 

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The fuel pump relay is ground triggered, you should see constant 12 volt power at the relay, the ecu sends a ground signal to the relay and triggers the relay. 

 

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On 10/7/2019 at 10:48 AM, acefuture said:

Alright well I finally got my car out of the trailer yesterday to start season prep, i know i know i know, i lagged....
Anyways, the car hasn't been started since April and has sat in the trailer since. Went to start it yesterday and put the key in the on position and the fuel pump didn't prime. Went to start it and crank crank crank, won't start, no fuel obviously. I check the fuel pump fuse, fine. Fuel pump relay, fine. Ignition fuse, fine. Power relay, fine. Everything powers up no problem. Put a hot wire from the battery straight to the fuel pump, works fine, but the car still won't start with the pump connected straight to the battery. So everything lead to the MEFI. I checked the grounds and they looked good. Checked any loose connections and lightly took the compressor to blow out all sand in the general area. Everything looks okay. So I'm assuming my MEFI took a dump over the summer. Is that a possibility? I bought it used from a guy last year who said it had been sitting on his shelf for years and he had no idea what the track record of it was. The fans don't work on the temp switch so it's kind of had issues since I bought it, but that's been it. So couple questions:

What else should I take a look at? @jjoseph99 had some good feedback and  said check the command wire for the fuel pump relay, which i'll take a look at tonight.
Any other thoughts to help diagnose?
Any one have a MEFI 4 or 4a lying around that I could borrow to plug in and see if that remedies the issue?
And if it does happen to be the computer, anyone have a MEFI 4 or 4a tuned for a stock LS1 or an LS1 with a mild cam they'd be willing to sell? Not looking for one tuned for a stroker or boost since I won't be doing either of those with this motor.

I have a Mefi tuned for a Turnkey ls1 that i would sell if you need one. Im doing a twin turbo build right now and am upgrading to and AEM setup.. 

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Do you have spark?--check for power at injectors.  If you have power at injectors if so than check for inj pusle with noid light.

Edited by danbalz
added more

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11 minutes ago, danbalz said:

Do you have spark?--check for power at injectors.  If you have power at injectors if so than check for inj pusle with noid light.

Yes, but even if I have spark it still won't start without fuel. And the pump isn't priming so that's the source of my issue.

I chased every single wire and check for 12v and continuity on everything. It's all good. So now I'm even more convinced it's the MEFI. Borrowing one from LRS tomorrow and will update with results.

Thanks for all the input from everyone 

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On 10/8/2019 at 2:36 PM, markcsand said:

The fuel pump relay is ground triggered, you should see constant 12 volt power at the relay, the ecu sends a ground signal to the relay and triggers the relay. 

 

I actually overlooked this when initially checking for power and ground. I was looking for 12v from ground side and wasn't realizing it's a ground triggered relay circuit. So thanks for the reminder. But it's not getting a ground signal from the computer, and the computers ground is fine. I even took it off the stud and cleaned it with a wire brush and chased it all the way back to the pin connector on J2

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Did you confirm +12v on the two pins as I said on the other forum?

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Well it was the MEFI. Borrowed another one from @L.R.S. And it started right up. Bummer that I need to get another one but at least it’s easily fixable. Thanks to everyone who chimed in with helpful advice 

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