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A good star quest mechanic


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#21 TFRACING

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Posted 19 October 2018 - 07:38 PM

View Postcroquest87, on 19 October 2018 - 04:06 PM, said:

Looks pretty good to me on compression part. Plugs do look kinda hot maybe not getting enough fuel? What's your fuel pressure? One thing at the time.
Need to check the fuel pressure tomorrow, need a gauge that reads higher than the one I have.





#22 TFRACING

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Posted 19 October 2018 - 07:40 PM

View Postscott87star, on 19 October 2018 - 04:09 PM, said:

Looks OK.  Once you move to non-stock injectors you have to raise the fuel pressure or idle and driveability will be poor.  Stock fuel pressure is 36-38 psi at idle, guys successfully running non stock injectors are in the 40's.  Maybe one of them will chime in, I tried and failed and went back to OEM, running twin secondaries with flex fuel.
Yes thats the problem I have right now, Idle was fine on OEM now runs like you know what with FIC replacement. Might go back to OEM if I can find a good secondary.

#23 TFRACING

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Posted 20 October 2018 - 02:12 PM

View Postcroquest87, on 19 October 2018 - 04:06 PM, said:

Looks pretty good to me on compression part. Plugs do look kinda hot maybe not getting enough fuel? What's your fuel pressure? One thing at the time.
Ok fuel pressure is right at 37. So that looks good too.

#24 ucw458

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Posted 20 October 2018 - 05:57 PM

Did You replace the FPR with an adjustable one?  If so try bumping the pressure to 45 psi.  

What year is your car and what are the flow rates for your replacement injectors?  Different years have different size injectors.  You could have the wrong size.
My 87
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#25 TFRACING

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Posted 22 October 2018 - 07:34 AM

View Postucw458, on 20 October 2018 - 05:57 PM, said:

Did You replace the FPR with an adjustable one?  If so try bumping the pressure to 45 psi.  

What year is your car and what are the flow rates for your replacement injectors?  Different years have different size injectors.  You could have the wrong size.
Its an 89, and they are 650 and 950. Stock FPG

#26 ucw458

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Posted 22 October 2018 - 08:38 PM

Well I have a couple of shot in the dark things for you to try but they are all injector related.


This normally isn't an issue but maybe injector resistance is causing issues.  Stock injectors are peak/hold type while all aftermarket replacements are saturated.  Meaning stock injector coil resistance should be around 2-3 ohms while aftermarkets will be 10-15 ohms.  Peak/hold equipped cars will have a resistor pack to increase injector resistance to protect the ECU from too much current draw on the injector circuit.  The stock resistor pack is around 8-10 ohms if I remember correctly.  That means the stock circuit should be 10-13 ohms and the aftermarket injectors puts it in the 18-25 ohm range.  On your setup that may be enough to cause voltage issues with the injectors.  Like I said normally this isn't an issue but every car is slightly different and age does weird things to cars.  To test this you need to find the resistor pack.  It's a silver and white thing about 3" long with 3 wires.  It's slightly behind the air filter box between it and the radiator.  It has 12v+ and one wire per injector.  The 12v- side of the injector is controlled by the ECU.  Short all 3 wires on the resistor pack together then try starting the car to see if it runs better.


Maybe you got a bad injector.  FIC has a good reputation but crap happens sometimes.  Take the OVCP (over valve cover pipe) off so you can look down the TB to see the injectors spray.  Next power the fuel pump with the test port.  Single wire going to nothing next to the cruise control actuator.  Then pulse the injectors with a 9v battery so you can see the spray pattern.  Should be a clean 15 deg cone.  Any dripping or streams means a bad injector.
My 87
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#27 TFRACING

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Posted 10 November 2018 - 11:16 AM

View Postucw458, on 22 October 2018 - 08:38 PM, said:

Well I have a couple of shot in the dark things for you to try but they are all injector related.


This normally isn't an issue but maybe injector resistance is causing issues.  Stock injectors are peak/hold type while all aftermarket replacements are saturated.  Meaning stock injector coil resistance should be around 2-3 ohms while aftermarkets will be 10-15 ohms.  Peak/hold equipped cars will have a resistor pack to increase injector resistance to protect the ECU from too much current draw on the injector circuit.  The stock resistor pack is around 8-10 ohms if I remember correctly.  That means the stock circuit should be 10-13 ohms and the aftermarket injectors puts it in the 18-25 ohm range.  On your setup that may be enough to cause voltage issues with the injectors.  Like I said normally this isn't an issue but every car is slightly different and age does weird things to cars.  To test this you need to find the resistor pack.  It's a silver and white thing about 3" long with 3 wires.  It's slightly behind the air filter box between it and the radiator.  It has 12v+ and one wire per injector.  The 12v- side of the injector is controlled by the ECU.  Short all 3 wires on the resistor pack together then try starting the car to see if it runs better.


Maybe you got a bad injector.  FIC has a good reputation but crap happens sometimes.  Take the OVCP (over valve cover pipe) off so you can look down the TB to see the injectors spray.  Next power the fuel pump with the test port.  Single wire going to nothing next to the cruise control actuator.  Then pulse the injectors with a 9v battery so you can see the spray pattern.  Should be a clean 15 deg cone.  Any dripping or streams means a bad injector.

Problem fixed, purchased an adjustable FPG and set it at 47 and she runs good. Thanks for all the help.

#28 croquest87

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Posted 10 November 2018 - 11:48 AM

Glad you fixed it!




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