Electrical Fuel System Prolems. Stumped Please Help!!

89LX50Coupe · 06-09-2001, 10:56 AM

I have an 1989 LX 5.0 Coupe. Problem is when I turn the key on without starting it even, the fuel pump keeps running. The injectors are also injecting fuel to the motor. It will start but, it blows some light black smoke, bogs down, stalls, and if I try to drive it, it won't go over 1500 RPM, even on the floor. It just jerks and hesitates. Also, there is a popping noise coming from the engine, I think its intake backfiring. After it started this it did it for about 2 hours, then drove normal for about 15 minutes, then started to do it again. It finally died on me and wouldn't restart, so I replaced the ignition control module, and it started. But it continued to hestitate, jerk, and smoke. PLEASE HELP. I have replaced the Throttle Position Sensor, Ignition Control Module, Fuel Pressure Regulator, and the fuel pump is a couple months old. Next guess is the ECU. I'm open to any suggestions! Thanks The check engine light is also on, and I tried to use a code reader on it, but it wouldn't work.
Someone suggested replacing my ACT sensor. I read on the net where you can clean it off with alcohol, and I did this but it didn't help. The parts store was closed so I couldn't get a new one. Just wanted to see if anyone else has any ideas before I set out to another hard day infront on the autoparts store!! A friend works at the autoparts store, so THANK GOD, I can try the parts before I buy them!

So any more guesses would be greatly appreciated.

jimberg · 06-09-2001, 11:13 AM

If your injectors are injecting fuel when you turn the ignition on, there's something seriously wrong. What makes you think that it's injecting? The fuel pump shouldn't stay running, either. You may have a short somewhere. You may want to check your test connector. There's a lead on there that would cause the fuel pump to run if it's ground. You may also want to check the fuel pump relay under the seat. It may be fused or something.

It's probably best, though, that you take it in to the dealer. I know it defies everything we believe in, but sometimes it's just the best thing to do.

------------------
351W 89 Mustang GT Convertible

89LX50Coupe · 06-09-2001, 11:28 AM

I am not tottally positive that the injectors are injecting fuel, but that is what it sounds like. Kindof a little hissing noise coming from the motor. I was thinking that it might be that the fuel pump had shorted out, but if the fuel just kept running, would it really hurt anything. The FPR is new, so when the fuel lines reached 40 psi or whatever, wouldn't the FPR just send the fuel back to the tank? Plus, once the motor is on, doesn't the fuel pump run constantly. I let it set at an idle for 5 minutes or so too see if it would burn up the fuel and run ok, but it wouldn't. Could the ECU cause the injector to stay open, if th ECU was burned up. If the injectors stay open, then the fuel pump could not build up any pressure, and it would just keep running. I'm fairly new to cars, I'm only 18, so this is just a theory. But I asked everyone that walked in to the autoparts store all day, and no one had a clue! Including a couple mechanics. I think you may be right about taking it to a shop! I am really running out of patients. I am going to try a new ECU & check that fuel pump relay first though. You also said something about a test lead that might keep the fuel pump running, wheres it that located? Thanks alot!

Unit 5302 · 06-09-2001, 11:37 AM

The ECU or MAF is most likely bad.

The fuel pump relay is getting power KOEO, which it should only get the signal for a brief couple second time frame. You must not have let the injectors inject long, if you had, there should have been enough gas in the cylinder to hydro lock it.

Running poorly when your first start it means you can throw your emissions crap out the window. That gets ignored until the engine reaches operating temp.

There are a few different things that can cause your extreme rich running condition. Even fewer with the car to the floor.

-Mass Airflow Sensor
-Temp Sensor
-Computer also known as ECU, PCM
-Incorrect injector size. Do you have the stock orange 19lb injectors?

If you haven't replaced the injectors, I'd be suspect of the

-MAF
-ECU
I would say the temp sensor would be hard pressed to cause a condition that bad, especially when the engine is cold.

I don't know if the MAF is in the fuel pump relay circuits. I'd certainly be suspect of it more than the computer if it is. Usually the computer will at least work in open loop (wide open throttle).

[This message has been edited by Unit 5302 (edited 06-09-2001).]

89LX50Coupe · 06-09-2001, 11:44 AM

If the fuel pumping, when the lines reached 40 psi, wouldn't the FPR send the fuel back to the tank, instead of shooting it out the injectors?

89LX50Coupe · 06-09-2001, 11:47 AM

Excuse me, If the fuel pump keeps pumping

jimberg · 06-09-2001, 11:59 AM

Unit, A fouled ACT left me stranded at work. When I started the car it would idle okay, but once I got going it wouldn't let me get enough RPMs to get moving and then it would stumble and backfire.

Unit's right about your injectors probably not injecting. That's why I questioned it. Some people may actually have probed the wires to see if they were getting voltage.

That sound is the fuel wooshing through the fuel rails from the fuel pump running. You're correct that the fuel pump running shouldn't hurt anything since it does run all the time when the engine is on.

What did you replace the fuel pressure regulator with? A stock replacement or an adjustable? Did you remember to hook up the vacuum line to the FPR? If not, you'll run very rich at idle. The computer won't be able to adapt, either, since your relative fuel pressure will not be constant.

Give us a run down of your modifications and the events leading up to this problem? We don't know if it just started doing this one day, or you had some driveability issues that kept getting worse and worse. Did you do anything under the hood before it started doing this? Is your SPOUT connector installed?

The worst part of diagnosis is that there can sometimes be multiple problems that cause the same symptoms.

Unit said that emissions stuff probably isn't the cause since they don't come into play until the car is warm and at part throttle. That's true, unless there's a defect in one of the components or someone accidently hooked them up wrong.

Say, for example, you accidently hooked the EGR vacuum line to the FPR and the FPR line to the EGR. The EGR would get opened all the time because of uncontrolled vacuum and the fuel pressure regulator would be getting zero vacuum since EGR vacuum line is controlled and closed at idle, creating a high relative fuel pressure and a rich condition.

Another possibility is an EGR valve stuck open.

If you want, meet me in the chat room and we can discuss some possibilities. It may speed up the diagnosis process. I'll just login there and look for you. I'm at my computer doing stuff anyway.

------------------
351W 89 Mustang GT Convertible

89LX50Coupe · 06-09-2001, 07:09 PM

Thanks Everybody! I finally fixed it! Two days isn't too bad! It was the computer. Turned out that my performance chip burned up my ecu. When I put in the new ecu this morning, it started right up. I had put the chip in it. It started and ran okay, but the car was still blowing smoke. So we fiddled with it for a while, changed the spark plugs and stuff. Then just out of the blue decided to take the chip off, wahla! It now runs perfect! I dont have the factory chip though, so its running in open loop mode or whatever, but much better than not running at all! If any one has a factory chip they want to sell me fairly cheap give me an e-mail. It's for a 1989 Automatic 5.0 LX Notchback. Thanks alot!

jimberg · 06-09-2001, 07:22 PM

The ECU didn't come with a chip of its own? Maybe you can just go to a junkyard and get one.

------------------
351W 89 Mustang GT Convertible

joe4speed · 06-10-2001, 01:01 AM

I had a similar problem with my car before I swapped computers to convert to Mass air. I would drive just fine, but suddenly it would die, while the fuel pump was running constantly. If I let it sit for a while... more than 30 mins it would run fine, but was sure to do it again. As soon as I swapped computers, it never did it again, and I'm sure that was the culprit. I tried everything to try to fix this problem. Good luck, man, I hope you figure it out, I know it's a pain!

------------------
Joe! 1988 GT, 167,000 miles!!! 13.58@105mph Check out my listing! Click here! Or my website:www.joe4speed.com
99 Ninja ZX-6R:10.32@135mph!
1993 Olds Eighty Eight LSS 16.40@88.8mph

06-09-2001, 10:56 AM	#1
89LX50Coupe Registered Member Join Date: Jun 2001 Location: Conway, Ar, USA Posts: 9	Electrical Fuel System Prolems. Stumped Please Help!! I have an 1989 LX 5.0 Coupe. Problem is when I turn the key on without starting it even, the fuel pump keeps running. The injectors are also injecting fuel to the motor. It will start but, it blows some light black smoke, bogs down, stalls, and if I try to drive it, it won't go over 1500 RPM, even on the floor. It just jerks and hesitates. Also, there is a popping noise coming from the engine, I think its intake backfiring. After it started this it did it for about 2 hours, then drove normal for about 15 minutes, then started to do it again. It finally died on me and wouldn't restart, so I replaced the ignition control module, and it started. But it continued to hestitate, jerk, and smoke. PLEASE HELP. I have replaced the Throttle Position Sensor, Ignition Control Module, Fuel Pressure Regulator, and the fuel pump is a couple months old. Next guess is the ECU. I'm open to any suggestions! Thanks The check engine light is also on, and I tried to use a code reader on it, but it wouldn't work. Someone suggested replacing my ACT sensor. I read on the net where you can clean it off with alcohol, and I did this but it didn't help. The parts store was closed so I couldn't get a new one. Just wanted to see if anyone else has any ideas before I set out to another hard day infront on the autoparts store!! A friend works at the autoparts store, so THANK GOD, I can try the parts before I buy them! So any more guesses would be greatly appreciated.

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06-09-2001, 11:13 AM	#2
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	If your injectors are injecting fuel when you turn the ignition on, there's something seriously wrong. What makes you think that it's injecting? The fuel pump shouldn't stay running, either. You may have a short somewhere. You may want to check your test connector. There's a lead on there that would cause the fuel pump to run if it's ground. You may also want to check the fuel pump relay under the seat. It may be fused or something. It's probably best, though, that you take it in to the dealer. I know it defies everything we believe in, but sometimes it's just the best thing to do. ------------------ 351W 89 Mustang GT Convertible

06-09-2001, 11:28 AM	#3
89LX50Coupe Registered Member Join Date: Jun 2001 Location: Conway, Ar, USA Posts: 9	I am not tottally positive that the injectors are injecting fuel, but that is what it sounds like. Kindof a little hissing noise coming from the motor. I was thinking that it might be that the fuel pump had shorted out, but if the fuel just kept running, would it really hurt anything. The FPR is new, so when the fuel lines reached 40 psi or whatever, wouldn't the FPR just send the fuel back to the tank? Plus, once the motor is on, doesn't the fuel pump run constantly. I let it set at an idle for 5 minutes or so too see if it would burn up the fuel and run ok, but it wouldn't. Could the ECU cause the injector to stay open, if th ECU was burned up. If the injectors stay open, then the fuel pump could not build up any pressure, and it would just keep running. I'm fairly new to cars, I'm only 18, so this is just a theory. But I asked everyone that walked in to the autoparts store all day, and no one had a clue! Including a couple mechanics. I think you may be right about taking it to a shop! I am really running out of patients. I am going to try a new ECU & check that fuel pump relay first though. You also said something about a test lead that might keep the fuel pump running, wheres it that located? Thanks alot!

06-09-2001, 11:37 AM	#4
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	The ECU or MAF is most likely bad. The fuel pump relay is getting power KOEO, which it should only get the signal for a brief couple second time frame. You must not have let the injectors inject long, if you had, there should have been enough gas in the cylinder to hydro lock it. Running poorly when your first start it means you can throw your emissions crap out the window. That gets ignored until the engine reaches operating temp. There are a few different things that can cause your extreme rich running condition. Even fewer with the car to the floor. -Mass Airflow Sensor -Temp Sensor -Computer also known as ECU, PCM -Incorrect injector size. Do you have the stock orange 19lb injectors? If you haven't replaced the injectors, I'd be suspect of the -MAF -ECU I would say the temp sensor would be hard pressed to cause a condition that bad, especially when the engine is cold. I don't know if the MAF is in the fuel pump relay circuits. I'd certainly be suspect of it more than the computer if it is. Usually the computer will at least work in open loop (wide open throttle). [This message has been edited by Unit 5302 (edited 06-09-2001).]

06-09-2001, 11:44 AM	#5
89LX50Coupe Registered Member Join Date: Jun 2001 Location: Conway, Ar, USA Posts: 9	If the fuel pumping, when the lines reached 40 psi, wouldn't the FPR send the fuel back to the tank, instead of shooting it out the injectors?

06-09-2001, 11:47 AM	#6
89LX50Coupe Registered Member Join Date: Jun 2001 Location: Conway, Ar, USA Posts: 9	Excuse me, If the fuel pump keeps pumping

06-09-2001, 11:59 AM	#7
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Unit, A fouled ACT left me stranded at work. When I started the car it would idle okay, but once I got going it wouldn't let me get enough RPMs to get moving and then it would stumble and backfire. Unit's right about your injectors probably not injecting. That's why I questioned it. Some people may actually have probed the wires to see if they were getting voltage. That sound is the fuel wooshing through the fuel rails from the fuel pump running. You're correct that the fuel pump running shouldn't hurt anything since it does run all the time when the engine is on. What did you replace the fuel pressure regulator with? A stock replacement or an adjustable? Did you remember to hook up the vacuum line to the FPR? If not, you'll run very rich at idle. The computer won't be able to adapt, either, since your relative fuel pressure will not be constant. Give us a run down of your modifications and the events leading up to this problem? We don't know if it just started doing this one day, or you had some driveability issues that kept getting worse and worse. Did you do anything under the hood before it started doing this? Is your SPOUT connector installed? The worst part of diagnosis is that there can sometimes be multiple problems that cause the same symptoms. Unit said that emissions stuff probably isn't the cause since they don't come into play until the car is warm and at part throttle. That's true, unless there's a defect in one of the components or someone accidently hooked them up wrong. Say, for example, you accidently hooked the EGR vacuum line to the FPR and the FPR line to the EGR. The EGR would get opened all the time because of uncontrolled vacuum and the fuel pressure regulator would be getting zero vacuum since EGR vacuum line is controlled and closed at idle, creating a high relative fuel pressure and a rich condition. Another possibility is an EGR valve stuck open. If you want, meet me in the chat room and we can discuss some possibilities. It may speed up the diagnosis process. I'll just login there and look for you. I'm at my computer doing stuff anyway. ------------------ 351W 89 Mustang GT Convertible

06-09-2001, 07:09 PM	#8
89LX50Coupe Registered Member Join Date: Jun 2001 Location: Conway, Ar, USA Posts: 9	Thanks Everybody! I finally fixed it! Two days isn't too bad! It was the computer. Turned out that my performance chip burned up my ecu. When I put in the new ecu this morning, it started right up. I had put the chip in it. It started and ran okay, but the car was still blowing smoke. So we fiddled with it for a while, changed the spark plugs and stuff. Then just out of the blue decided to take the chip off, wahla! It now runs perfect! I dont have the factory chip though, so its running in open loop mode or whatever, but much better than not running at all! If any one has a factory chip they want to sell me fairly cheap give me an e-mail. It's for a 1989 Automatic 5.0 LX Notchback. Thanks alot!

06-09-2001, 07:22 PM	#9
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	The ECU didn't come with a chip of its own? Maybe you can just go to a junkyard and get one. ------------------ 351W 89 Mustang GT Convertible

06-10-2001, 01:01 AM	#10
joe4speed He said Member...heh, heh Join Date: Sep 1999 Location: Jupiter, Florida U.S.A. Posts: 3,718	I had a similar problem with my car before I swapped computers to convert to Mass air. I would drive just fine, but suddenly it would die, while the fuel pump was running constantly. If I let it sit for a while... more than 30 mins it would run fine, but was sure to do it again. As soon as I swapped computers, it never did it again, and I'm sure that was the culprit. I tried everything to try to fix this problem. Good luck, man, I hope you figure it out, I know it's a pain! ------------------ Joe! 1988 GT, 167,000 miles!!! 13.58@105mph Check out my listing! Click here! Or my website:www.joe4speed.com 99 Ninja ZX-6R:10.32@135mph! 1993 Olds Eighty Eight LSS 16.40@88.8mph