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Premium Member
2003 Chevy SSR
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1,450 Posts
Discussion Starter #1
Big question: What should the fuel pump be doing when the key is turned to "on?"

Longer question: Ilsa has had a lot of work done lately. She got a new Magnuson 2300 supercharger (to replace her 120) and Kook's headers. Her exhaust system was redone, but it's pretty much the same custom true-dual system that was on before the headers. Her power steering was so close to the headers that it blew a hose, so I had to have the hoses rerouted away from the headers. After that, all she needed was a tune, but it was too cold to do it outside and we couldn't find an indoor dyno that was available. FINALLY, it was over 50 degrees yesterday, so we got the chance to do a street tune. Now she sounds great and has a lot of jump, but starting is a major problem.

When the key goes on, I can hear a faint electric motor which I assume is the fuel pump; but what happens next sounds like the engine isn't getting enough fuel to start. It goes like this:
1st crank - nothing
2nd crank - nothing, or maybe one hit
3rd crank - a couple hits
4th crank - a few hits, then a very rough start which finally becomes smoother

This sounds to me like the engine isn't getting much fuel during the start.

Does this sound a problem with the tune, or possibly a defective fuel pump (aftermarket Aeromotive)?
Can the computer be tuned to get more gas to the engine on startup? Again, it does fine after the engine finally gets going.
 

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BAD BOW TIE
Joined
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11,388 Posts
Mine did that and it ended up it was the Mass Air Flo Sensor wasn't reading right on start up. You can clean them with a spray cleaner after you remove it. Can not be done installed. Or you can replace it. That is what I did. Starts and runs awesome now.

I suspect it is in the air fuel ratio area at start up because it didn't do it until the tune or the work done. Any codes or check engine lights???

Good luck.
 

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Premium Member
2003 Chevy SSR
Joined
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1,450 Posts
Discussion Starter #3
I was getting an occasional misfire engine light after the tune, but it wasn't showing up on the tuner's software, and eventually went away. I'm pretty sure that the plugs are not in good shape after running very rich until the final tune. This MAF is only a year or two old.


Mine did that and it ended up it was the Mass Air Flo Sensor wasn't reading right on start up. You can clean them with a spray cleaner after you remove it. Can not be done installed. Or you can replace it. That is what I did. Starts and runs awesome now.

I suspect it is in the air fuel ratio area at start up because it didn't do it until the tune or the work done. Any codes or check engine lights???

Good luck.
 

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BAD BOW TIE
Joined
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11,388 Posts
I was getting an occasional misfire engine light after the tune, but it wasn't showing up on the tuner's software, and eventually went away. I'm pretty sure that the plugs are not in good shape after running very rich until the final tune. This MAF is only a year or two old.
The tinny wires in them are very delicate and it doesn't take much dirt or oil to foul them up and make them give crazy readings for the air fuel mixture. The spray cleaner stuff is only a couple of bucks for a spray can at a parts store. Just take off the mass air sensor and spray it as directed and put it back on when dry. Cheapest thing to start with. If that fails ask the tuner guy what he thinks. Again you said it worked ok before the tune so I would work from there backwards. Good luck.
 

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Supporting SSR Hobbyist
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10,190 Posts
Measure the fuel pressure on the fuel rail while cranking....... This will definitely help isolate a section of the fuel system. It will tell you if there is a problem in the fuel supply to the injectors....

Regards,

Mike
 
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