boost gauge on when car isnt running???
05-29-10, 07:48 PM
#1
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boost gauge on when car isnt running???
87 turbo with and S5 motor in it. Still using S4 harness. Whenever i have the boost pressure sensor plugged in the boost gauge maxes out with the key on but car isnt running. if i unplug it it shuts off. Car wont run without boost sensor plugged in but wont run WITH it plugged in for some reason either!!!
Tried tracing the wires back to the ECU and everything seems to be in the right spot and no cracked or grounded out wires. The main wire I cant figure out is a brown with a black stripe going from the ECU to the boost pressure sensor. If i disconnect just that wire the boost guage goes normal but car still wont start.
searched and couldnt find anything.
Tried tracing the wires back to the ECU and everything seems to be in the right spot and no cracked or grounded out wires. The main wire I cant figure out is a brown with a black stripe going from the ECU to the boost pressure sensor. If i disconnect just that wire the boost guage goes normal but car still wont start.
searched and couldnt find anything.
05-30-10, 04:50 AM
#2
S4 boost sensor? Did the boost gauge and engine run right when it had a S4 engine in it?
You could completely unplug the boost sensor on an S4 car, and that won't keep it from starting. The boost sensor isn't your no-start problem. Are you getting fuel? You say you have an '87 car... well an S5 is obviously 89-92 car... injectors are different from 88-92. They changed from low impedance injectors 84-5/87ish to high impedance injectors from 87.5ish-92. You're not gunna get high impedance S5 injectors to fire on an 87 S4 harness. Easy thing to do is put your 87 turbo injectors in your S5 engine. OR, maybe I'm just talking about something that doesn't even apply to your setup. Define "S5 motor". How S5 is the engine you have in your car. For instance, the engine in my 87 TII is 90% S5... and a little S6 and mod. But I'm running low impedance injectors in the engine since my 87 has the injector resistor packs near the boost sensor area. Will probably get a 88 harness and make it high some day so I can get a more broad selection of injectors, but my project is a different story.
Anyways, what do you know about my questions? I'll help you along with this problem.
You could completely unplug the boost sensor on an S4 car, and that won't keep it from starting. The boost sensor isn't your no-start problem. Are you getting fuel? You say you have an '87 car... well an S5 is obviously 89-92 car... injectors are different from 88-92. They changed from low impedance injectors 84-5/87ish to high impedance injectors from 87.5ish-92. You're not gunna get high impedance S5 injectors to fire on an 87 S4 harness. Easy thing to do is put your 87 turbo injectors in your S5 engine. OR, maybe I'm just talking about something that doesn't even apply to your setup. Define "S5 motor". How S5 is the engine you have in your car. For instance, the engine in my 87 TII is 90% S5... and a little S6 and mod. But I'm running low impedance injectors in the engine since my 87 has the injector resistor packs near the boost sensor area. Will probably get a 88 harness and make it high some day so I can get a more broad selection of injectors, but my project is a different story.
Anyways, what do you know about my questions? I'll help you along with this problem.
05-30-10, 03:13 PM
#3
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Traditionally the BRS doesn't have any interaction, at all, with a vehicle's starting ability. Secondarily, the boost gauge should be VACUUM-driven, and not electrical... Ergot, if it's unplugged, it should read at +/- 0 -/+ (0 ratio between the engine and outside, ambient). If it's elecronically-controlled, there STILL shouldn't be anything affecting the start-up....
Nothing less than a short would cause that.... Or, depending on if you're trying to just pull the vac-line (suggested check), and start the car, there could be some other issue(s).
Nothing less than a short would cause that.... Or, depending on if you're trying to just pull the vac-line (suggested check), and start the car, there could be some other issue(s).
05-30-10, 06:45 PM
#4
... the stock boost gauge in the gauge cluster is indeed electric and is run off the boost sensor and a vac line goes to the boost sensor. However, the car doesn't even need the boost sensor plugged in to start or even run. It will actually run just fine without it plugged in. Boost sensor, not the starting problem.
06-01-10, 02:57 PM
#6
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If the boost/pressure sensors volt ref signal is shorting ouit.............then the ECU won't make spark 'cause the ECU NEEDS the volt ref signal/output to make spark. NOT saying the boost/pressure sensor being/not being plugged in will/will not let a engine start.
I'm saying that if the volt ref signal on ANY of the sensors is grounded out, it KILLS the ability of the ECU to make spark. I'd unplug the boost sensor......afm........tps etc and see if you NOW have spark or not.
A more sensible approach would be to put the key to ON and take a meter and see if the brown/white wire on any of the sensors has 4.5 to 5vdc on it. Pick any sensor with the brown/white wire. Matters not which. They are all tied or spliced together inside the EM harness. NO 4.5 to 5vdc means that engine isn't going to start at all.
I'm saying that if the volt ref signal on ANY of the sensors is grounded out, it KILLS the ability of the ECU to make spark. I'd unplug the boost sensor......afm........tps etc and see if you NOW have spark or not.
A more sensible approach would be to put the key to ON and take a meter and see if the brown/white wire on any of the sensors has 4.5 to 5vdc on it. Pick any sensor with the brown/white wire. Matters not which. They are all tied or spliced together inside the EM harness. NO 4.5 to 5vdc means that engine isn't going to start at all.
06-04-10, 01:44 PM
#7
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ok tested the brown/white wire. Has 4.95 volts and now i'm randomly getting spark. Then i lost fuel. So i pulled the fuel pump and tested it and it was fine. Then put the fuel pump back in and now i'm randomly getting fuel again.... i hate this car.
SOOOO i have spark and fuel. Air is obvious. But my boost gauge is still maxed out and my oil pressure gauge is maxed out and i dont know why. Oh and the car WONT F-ING START!!!
now heres another weird thing. If i hold the starter on while someone is pinching off the fuel line the car will start and get up to about 2k RPMS untill i let off the starter and the car dies.
8 years of working on Rx7's and never had so many problems!!!
halp!!
SOOOO i have spark and fuel. Air is obvious. But my boost gauge is still maxed out and my oil pressure gauge is maxed out and i dont know why. Oh and the car WONT F-ING START!!!
now heres another weird thing. If i hold the starter on while someone is pinching off the fuel line the car will start and get up to about 2k RPMS untill i let off the starter and the car dies.
8 years of working on Rx7's and never had so many problems!!!
halp!!
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