Check Engine light still on...

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Jan 18, 2018 | 09:06 AM

quadracerx

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From: Graham WA.

Check Engine light still on...

I finally got a chance to work on the car again!! I put a fuel pressure gauge in line between the two throttle bodies and get between 15-17 Lbs of pressure with the car running....

So now I still have the "Check Engine Light" and it is hard starting sometimes I have to pour a small dash of fuel into the throttle bodies but then it starts right up?

So its not fuel pressure, no codes with a Snap On MT2000 Scanner, no codes with the "Paper Clip method"?

So now Im wondering if it could be my MAP sensor or the IAC valves?

Any help you can provide would be great as Im at a loss as to what to do next?

Thanks,

Steve

Jan 18, 2018 | 09:53 AM

scotth48

Burning Brakes

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From: Charlotte Michigan

What year are we working on?

Jan 18, 2018 | 10:46 AM

quadracerx

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From: Graham WA.

Oh... Sorry I guess that would help...LOL

1984 with Crossfire Injection... all stock

Thanks,

Steve

Jan 18, 2018 | 03:27 PM

billschroeder5842

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From: Southlake, TX

With the XFire check your Throttle Position First. The setting should be at .525.

The fact that you can pour gas and fire it off tells me the (first) step is check your TPS setting. After that, IAC, MAP sensor...etc.

Jan 18, 2018 | 05:17 PM

1984Z51auto

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From: Denver Colorado

Not clear why the Check Engine Light would be "ON" with no codes set. However, your hard start issue could be the fuel pump relay. If you have an extended cranking period prior to the engine firing off, does the fuel pump run when you turn the engine "ON" prior to cranking it? Check the fuel pressure with your gauge on a cold start, ignition "ON" without cranking. It should rise to 13 psi and then drop back to 0 psi when the pump stops after about 5 secs. Then turn engine "OFF" and attempt to start it. Pressure should rise immediately to 13 PSI and stay there while engine runs. If you have to crank the engine for a long time prior to seeing a fuel pressure increase the pump relay is suspect. The L83 engine uses an oil pressure switch as a backup to the fuel pump relay to turn on the pump but, it takes a bit of cranking to work. Sorry about the windy answer... it just takes a bit to go thru the workings!

Jan 19, 2018 | 07:03 PM

quadracerx

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From: Graham WA.

Where is the fuel pump relay located?

How do I test my or measure my Throttle position Sensor?

Will either of these cause the "Check Engine Light" to come on?

Thanks for all your help..

Steve

Jan 20, 2018 | 03:55 PM

1984Z51auto

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From: Denver Colorado

Quote:

Originally Posted by quadracerx

Where is the fuel pump relay located?

How do I test my or measure my Throttle position Sensor?

Will either of these cause the "Check Engine Light" to come on?

Thanks for all your help..

Steve

The Fuel Pump Relay is located in the engine compartment to the immediate left of the wiper motor, held on with 2 nuts if I remember right.

To test the TPS you need a digital multi-meter and a jumper harness or you can probe the connector from the back side. Initial reading should be 0.525 volts between terminal A and B (A is bottom, B is middle on the TPS, ignition on not running). Then slowly open throttle and ensure that readings move smoothly throughout the range. A jump, dead spot or plateau is a bad TPS.

A bad TPS circuit could set trouble codes 21 or 22 and turn on the Check Engine Light.

Hope this helps, I'm going from memory as I no longer have an 84 FSM. When I still had my 84 I did a lot of this however! I recommend a real 1984 GM service manual as there are a lot of unique things about a Cross-Fire.

Jan 20, 2018 | 08:00 PM

billschroeder5842

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From: Southlake, TX

Quote:

Originally Posted by 1984Z51auto

Not clear why the Check Engine Light would be "ON" with no codes set.

That one has me perplexed too......

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Jan 20, 2018 | 08:30 PM

1984Z51auto

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From: Denver Colorado

Quote:

Originally Posted by billschroeder5842

That one has me perplexed too......

Yes, very strange to get a Check Engine Light only with no codes. I guess the ECM could be bad but I've never seen it happen that way.

Jan 20, 2018 | 11:44 PM

#10

quadracerx

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From: Graham WA.

I forot to mention I already replaced the ECU with a "rebuilt" one...

Check engine light still on...

I ordered a TPS test harness and new TPS Module.... So we will see... Still a bit unclear as to how to adjust it?

Thanks for all the help..

Steve

Jan 21, 2018 | 10:32 AM

#11

1984Z51auto

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From: Denver Colorado

Quote:

Originally Posted by quadracerx

The TPS turns on its mounting screws. With the ignition "ON" and not running twist it until the multi-meter shows 0.525 volts between terminals A and B and tighten it up.

Jan 22, 2018 | 02:59 PM

#12

quadracerx

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From: Graham WA.

Ok... I will let you know when I get the TPS and the "Tester" setup.

Thanks again, for all the help!!

Steve

Jan 23, 2018 | 10:54 PM

#13

kael

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Quote:

Originally Posted by 1984Z51auto

Yes, very strange to get a Check Engine Light only with no codes. I guess the ECM could be bad but I've never seen it happen that way.

Should see code 12 at least, otherwise something is wrong with ECM. Could also be connections to the ECM. If no code at all is shown, remove the ECM, battery disconnected first, and remove/insert MEMCAL, carefully. Same for cables to ECM, remove and install a couple of times. Then recheck.

After disconnecting battery, press brake for 10 seconds, reconnect battery, is the Check light still on? That would also point to ECM.

(guys, don't go off about pressing brake, I know. Worth doing with a big problem, it's 10 seconds. And, ya know.)

Last edited by kael; Jan 23, 2018 at 10:55 PM. Reason: cables, right

Jan 23, 2018 | 11:49 PM

#14

quadracerx

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From: Graham WA.

The "Check Engine Light" was on with the original ECU.. I thought that maybe the ECU was bad and causing the Check Engine Light. So I replaced it with a Reman ECU and still have the Check Engine Light....

I will try the "Press brake for 10 seconds" before reconnecting battery and see if that does anything and I will disconnect and reconnect the ECU and cables... And try re-seating the EPROM too...

At this point Im lost... But I cant work on the car for at least a week, hopefully the TPS Tester will show up and I can check that too...

My plan is to use the tester first to take a reading on the current TPS then if adjustment is needed try that...

If I need to replace the TPS I will...

If none of that changes the "Check Engine Light" situation then I will try the ECU re-seating, brake pedal thing...

Thanks so much for everyone's help... This Check Engine Light thing is crazy...LOL

Steve

Jan 24, 2018 | 11:36 AM

#15

1984Z51auto

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From: Denver Colorado

Quote:

Originally Posted by quadracerx

Does the car run alright with the Check Engine Light on? I'd be tempted to take the bulb out!

Jan 24, 2018 | 02:13 PM

#16

quadracerx

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From: Graham WA.

It runs fine... has a slight miss but I think I need to set the timing...

And trust me I havent ruled out pulling the bulb... Just want to exhaust all the options first...

Thanks,

Steve

Jan 25, 2018 | 01:59 PM

#17

1984Z51auto

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From: Denver Colorado

It is very odd to have a Check Engine Light without codes.

Jan 29, 2018 | 09:58 PM

#18

quadracerx

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From: Graham WA.

TPS Testing Harness showed up today!! I wont be able to work on the car until later in the week, but have the tester a new MAP sensor and new TPS.... My plan is to run a test on the existing TPS depending on results replace the TPS if needed... IF Check Engine Light goes away... We are good...

If not replace MAP sensor... If Check Engine Light is still on after all this...

I will pull both TBI units and have them rebuilt... They need it anyway, the rebuilder says he can test my existing IAC motors... If they need replacement then so be it...

Hopefully through all this the Check Engine Light goes away... IF NOT...Im pulling the bulb... Since I have to send the Digital Dash in for repair, it should be easy..LOL

I appreciate everyones help and advice through everything... This group is great!!

Steve