VX died Help....

[bcbike]

Help.....I was sitting at a stop when the engine shut completely off. It turned over but would not restart like it was not getting fuel. O towed it home and threw a fuel pressure tester on the fuel rail and with the key on I had zero pressure. I jumped the fuel pump relay and had then had 48 lbs of pressure. Its seems the fuel pump is working. I also noticed the fuel gauge reads below empty with no movement when I turn on the key, (i have 1/2 tank of fuel), also no check engine light with the key on. No fuel pressure when I attempt to start it. Fuel pressure when I jump the relay, no fuel gauge and no check engine light. Prior to this no problems, I'm stumped.

[Triathlete]

Bad relay?

[bcbike]

I thought that too so I replaced the relay with no luck.

[pbkid]

fuel gauge went out half way through a tank, but you didnt notice? i know it seems obvious, but its worth a try. I've heard of many gauges going out and people going through all kind of diagnostics before they throw a gallon of gas in it...

[bcbike]

I thought of that too and dumped in 5 gallons. It's strange, I have fuel and pressure when I jump the relay but no fuel pressure when I try to start it.

[yellowgizmo99]

someone had to bend the pins that the relay plugs into, might check into that.

[bcbike]

I tightened up the connections where the relay plugs in still no luck.

[VxSport]

The only thing I can think of is ground wire on or around the tank. How much rust is on your frame and tank. Might be worth pulling the float and sender unit from the rear side of tank and inspecting it and related wiring.
This only makes sense for the gauge, I don't think it would kill the engine, unless it reports a failure to the PCM on the float.
Still checking book though..... good luck

[bcbike]

Not much rust on the frame or tank but the ground thing is definitely worth checking out.
Thanks.

[pbkid]

It cranks but doesnt start? Have you checked the distributor?

Ground cable on the battery?

[Triathlete]

No distributor on a VX ;) If battery ground was bad probably would not crank.

[bcbike]

I scoured the VX for every ground bolt on the body I could find polishing up the contact points. No luck.

[vt_maverick]

Time for a young priest and an old priest...

[Triathlete]

Do you have a voltage meter? You may not be getting voltage to the relay to activate it. You should have voltage at 2 pins...the one you jumped which powers the fuel pump and another that only has power when the ignition is on (this activates the relay allowing power to the pump). If there is no power there then you can backtrack. Have you checked fuses?

[bcbike]

Fuses are good. I'm pretty sure I'm not getting anything to the relay when the key is on I will throw a meter on to confirm.

[Scott Larson]

One thing you should include in your troubleshooting is the ignition switch. They can take a real beating with a heavy set of keys or oversized/heavy keyfobs. There's alot of small contacts doing alot of important things in that little buggar! Best of luck and please do keep us posted...:thumbup:

[bcbike]

Still dead:(
In short here is what I have done:
Jumped the fuel pump relay and the fuel pump tested OK, pressure at the fuel rail.
Checked all fuses.
Checked the ECM relay.
Cleaned and polished all of the ground connections that I could find.
Checked all of the connections I could find on the wiring harness.
Confirmed I had good ground circuits to the ECM.
Confirmed I had a good ignition circuit to the ECM
Confirmed I had a good battery circuit to the ECM.
Confirmed the injectors are not firing.
Jumped the check engine light to confirm the bulb is not dead.
Still will not start, I can jump the fuel relay to get the pump to work. I do not have a check engine light with the key on and no fuel gauge with a 1/2 tank of fuel. :madb:

[Triathlete]

Do you have a scan gauge or a code readee you can use to check for codes?

[Maddawg]

Ok, you've narrowed it down to either fuel or electical. Can you pour some fuel down the the injector body and see if it starts momentarily?? You might also spray some fuel or starter fluid into each cylinder, I know its a lot of trouble but maybe worth it.

[bcbike]

A shot of starting fluid and it fires. I threw a code reader on but it will not connect to read a code.

[Maddawg]

A shot of starting fluid and it fires. I threw a code reader on but it will not connect to read a code.

Ok, so now we know its not an ignition problem, you've got spark. Not compression issue either. So again its fuel. Its not getting there for a couple of reasons. The suspected fuel relay or a plugged fuel line. Disconnect the fuel line before the fuel filter (between the gas tank and the injector body). Start it and see if any fuel pumps into a jar.

[Maddawg]

Was this the procedure you used to check the fuel pump relay?

To troubleshoot a fuel pump relay, start by pulling the relay out of its socket. Use a circuit tester and check the pins in the socket for power with the ignition key off. There should be one pin that has power direct from the battery. If not, check the fuse and make sure that there is power to the fuse. If not, look for the main wire in the fuse block to be loose or open to the fuse. If the fuse is okay and the relay has power to the one pin, turn the ignition key on.

Check to see if there is power to two terminals now. This will require someone else to help because the computer will shut the power off to the relay in 2 seconds if it does not sense the engine starting. This is so that if the switch is turned on, the fuel pump does not keep running. In an accident, the pump will also shut off when the engine dies. Have someone turn the key on and off with 5-second delays while the pins are checked for power to a second terminal. If there is no power, then there is a problem with the line to the ignition switch or a security problem.



This is a problem with the key recognition or if the security system is engaged. If there was power to the second terminal, check the relay with two jumper wires. Put one wire from the positive battery terminal to the relay battery terminal. If this terminal can't be read, put it to any terminal. It won't hurt anything. Run the next lead from the negative terminal of the battery to the relay. With the positive lead attached to a pin on the relay, touch the negative lead to the other terminals. Listen for the relay to click when activated. If it does not click, move the positive lead to a different terminal and try again. If the relay will not click and activate, the relay is bad.

If the relay clicks, then the problem is elsewhere. Use a volt and ohmmeter for the next test. Put the meter on ohms. Remember which terminals have power because to check those terminals with an ohmmeter would ruin the ohmmeter. Look for the terminals without power. Check them for a good ground. If there is no good ground, take the fuse block loose and look under the fuse block for a loose wire or burnt wire. Cut the ground wire and make a new ground wire to the chassis.

If there was a good ground, then insert the relay back in and have someone turn the key on and off and the relay should click. If not, then the computer is at fault. If it clicks, then pull the electrical connector loose for the fuel pump located right behind the fuel tank. Have someone turn the key on and off again while checking for power at the fuel pump. If there is no power, there is an open (bad wire) in the wire leading to the fuel pump. If there is power, the fuel pump is bad.



Read more: Troubleshooing a Fuel Pump Relay | eHow.com http://www.ehow.com/how-does_4796259_troubleshooing-fuel-pump-relay.html#ixzz2D6ab8EX9

[Cris]

I also had a similar problem. Good fuel pressure at idel, but at road speed lost all pressure,check it that way if you can

[VxSport]

I had a chevy s10 a few years ago.... In that vehicle. normal operating fuel pressure is about 62 psi, however it also requires a minimal pressure of 56 psi to let the vehicle start.

[evillecutter]

i had this exact same problem lately - i thought i had a bad relay but it turned out it was the connection between the fuse box and the fuel pump relay -if you can get it to start see if your fuel pump relay gets hot - if it does it means its either bad or isnt getting a good connection - i took mine apart and it looked perfect inside so i sanded down all the contact points both on the relay and inside the fuse box (mine was the post most towards the firewall that wasnt getting good connection) that was a week ago and it hasnt got hot since and has been running much better

[tom4bren]

I threw a code reader on but it will not connect to read a code.

That's not good. The code reader should be able to connect to the computer even if the vehicle is not running.


... This will require someone else to help because the computer will shut the power off to the relay in 2 seconds if it does not sense the engine starting. This is so that if the switch is turned on, the fuel pump does not keep running. In an accident, the pump will also shut off when the engine dies. ... If there is no power, then there is a problem with the line to the ignition switch or a security problem. ... then the computer is at fault.

The fact that the code reader isn't talking to the computer and that the relay is functioning but not getting signal, I think your problem lies with the computer. Unfortunately I don't have a solution for you other than replacing the computer.


i had this exact same problem lately - i thought i had a bad relay but it turned out it was the connection between the fuse box and the fuel pump relay -if you can get it to start see if your fuel pump relay gets hot - if it does it means its either bad or isnt getting a good connection - i took mine apart and it looked perfect inside so i sanded down all the contact points both on the relay and inside the fuse box (mine was the post most towards the firewall that wasnt getting good connection) that was a week ago and it hasnt got hot since and has been running much better

This seems like the next logical step to take (short of replacing the computer).

[bcbike]

Ok. I ran out of options. Found a used computer on Ebay should be here in a few days. My fingers are crossed.

[tom4bren]

Holy crap on a cracker ... I didn't know that you were gonna jump in with both feet on my recommendation. Hope that's what the problem is.

Keep your old 'puter. There are companies online that can fix them (haven't checked specifically for the VX though).

[Maddawg]

Ok, so now we know its not an ignition problem, you've got spark. Not compression issue either. So again its fuel. Its not getting there for a couple of reasons. The suspected fuel relay or a plugged fuel line. Disconnect the fuel line before the fuel filter (between the gas tank and the injector body). Start it and see if any fuel pumps into a jar.



Thats why I was hoping to take the fuel pump out of the equation.

[tom4bren]

Fuel pump is working. He gets pressure at the fuel rail if he jumps the relay. Basically; he's getting power & ground to the relay, the relay functions if jumpered, he's just not getting signal to it from the computer.

[Y33TREKker]

Checked the ECM relay.

Confirmed I had good ground circuits to the ECM.
Confirmed I had a good ignition circuit to the ECM
Confirmed I had a good battery circuit to the ECM.
Confirmed the injectors are not firing.
...
Which relay are you referring to when you say ECM?

Are you talking about the one in the manual's diagrams labeled "PCM Main Relay" in the fuse/relay box in the engine compartment?

If not, that's one possible culprit. Another would be the 40Amp EB18 "PCM" fuse in the same fuse/relay box.

The PCM relay would be affecting the powertrain control module, the fuel pump relay, and the fuel injectors.

[bcbike]

Correct PCM. I checked both relay and fuses both are good.

[bcbike]

I Should start a new post "what would you buy if your VX died":bgwo:

[Maddawg]

I also noticed the fuel gauge reads below empty with no movement when I turn on the key, (i have 1/2 tank of fuel), also no check engine light with the key on. No fuel pressure when I attempt to start it. Fuel pressure when I jump the relay, no fuel gauge and no check engine light. Prior to this no problems, I'm stumped.

Any chance there is a fuse out somewhere?

[Mile High VX]

I Should start a new post "what would you buy if your VX died":bgwo:

http://www.vehicross.info/forums/showthread.php?t=21239&highlight=replacing+VX

Go ahead...join the fun!

[Leon R]

Typically, ECU does not turn on the fuel pump until you start cranking. That is when it sends a signal to fuel pump relay to turn on. Have you checked if your FP relay is getting such signal?

Has your "scanner" worked previously, when VX was running well? If so, and now your scanner can not connect, I would also suggest a bad computer. But... if your computer is so messed-up that it will not connect and will not run fuel pump/injectors, it is unlikely that it would fire the ignition... So something doesn't add up here.

[tom4bren]

... if your computer is so messed-up that it will not connect and will not run fuel pump/injectors, it is unlikely that it would fire the ignition...

It may not be as surprising as you might think.

The fuel pressure relay activation is considered part of a safety critical circuit. In the event of an accident, that relay is supposed to be disabled to prevent fuel from being sprayed around & creating a fire hazard. Safety critical software is typically compartmentalized & isolated from the rest of the operating system. The ignition & starter would not be considered safety critical.

That does bring to mind a surprising thought though (surprising because I thought of it:)). What is the sensor that shuts down the fuel system in the event of an accident & could that be his culpret?

[Ldub]

Typically, ECU does not turn on the fuel pump until you start cranking. That is when it sends a signal to fuel pump relay to turn on. Have you checked if your FP relay is getting such signal?

Maybe in a "typical" vehicle...:smilewink

I can hear mine pressure up as soon as the ign is in the on pos, before any cranking over of the engine.

[Scott Larson]

Tom, you're referring to the rollover sensor. When it's faulty it shuts down the fuel pump as it would in case of vehicle rollover...

It's default mode is "off".

[tom4bren]

Tom, you're referring to the rollover sensor. When it's faulty it shuts down the fuel pump as it would in case of vehicle rollover...

So the fuel is only shut off in the case of a roll over ... not for front impact. That's not a very enginerddy approach to safety.

[Scott Larson]

The name is a bit of a misnomer, as you are correct, in "severe" impacts it is supposed to shut the pump down regardless of the orientation of the vehicle, "supposedly"...

[Dmitrikr]

did he mention no pulse on injectors? camshaft sensor fault-?

[tom4bren]

HMMM ... wonder if it's controlled by the airbag sensor.

bcbike - is your SRS lite on?

[tom4bren]

did he mention no pulse on injectors? camshaft sensor fault-?

He gets no pressure at the fuel rail (unless he jumps the relay) so it's not that.

Rekin we should just table the discussion till he gets his new 'puter & tries it out.

[Leon R]

did he mention no pulse on injectors? camshaft sensor fault-?

That is what I was thinking, but why would it fire the coils? Usually spark goes along with the fuel.

[Scott Larson]

I second that Tom, but your airbag ? is intriguing...

[Dmitrikr]

That is what I was thinking, but why would it fire the coils? Usually spark goes along with the fuel.

crankshaft sensor - sending rpm signal and TDC#1 to pcm - if no crank signal - no fuel pressure. also pcm fires coils up according crank signal. camshaft for injectors and better correlation etc...
But, with the key on-run pcm should send signal to fuel pump to prime fuel for a second or two.

[bcbike]

I installed the "new computer" didn't help.
Fuses good
Ground circuit to the PCM terminal connections good
All relays good.
Checked all wiring connectors
Polished all ground points to body
No Check Engine- light will not even light up--- very strange
No Fuel gauge--- also very strange.
Pressure at the fuel rail.
Injectors do not fire
Will hit with a shot of starting fluid. :confused:

[Triathlete]

Check your wire looms...especially where they pass through bulkheads. Also your relay could still be bad...with the ignition on you should have power at 2 pins. If you have power at 2 pins with the ignition on then its a bad relay. If you only have power at 1 then you need to start looking at wiring and components.

[bcbike]

One question i have is where does the fuel gauge and check engine light fit into the picture. The fuel gauge does not work and the check engine light will not even light when the key is on. (bulb is good).

[Dmitrikr]

One question i have is where does the fuel gauge and check engine light fit into the picture. The fuel gauge does not work and the check engine light will not even light when the key is on. (bulb is good).

ground wire for cluster might be.

[Scott Larson]

I'm still inclined to think it may be the ignition switch. You can easily check each contact point with an ohm meter. If any show an open circuit when swithched on, I believe you will confirm if it is the problem. Tom4bren also brought up a valid possibility of it being the rollover sensor, once again easily confirmed with an ohm meter...Dig into the online shop manual for guidance to both. Best of luck, I know it's gotta be gettin' old by now!
:_brickwal :_mecker: :_confused

[FenderBender]

Just throwing this out there. If it would be a bad fuel level sensor (float) telling the gauge and computer it is out of fuel. Would the computer shut the fuel pump off so it does not run dry and burn itself out? Maybe for safety so the pump does not overheat inside a empty tank filled with gas fumes?

[Maddawg]

Just two questions. (1) What was the last thing that you had done before this problem?? (2) Did you change the fuel cap?? Theres a vacuum and pressure valve in it.

[bcbike]

OK...This morning got deep into the wiring under the dash. Checked all of the connections moved wires around tightened up and cleaned everything I could find and........it started.

Not sure exactly what was loose but she is alive. :bgwb::clap:
It was most definitely a wiring or connector problem I just wish I knew exactly what I did.

Bunches of thanks to everyone who offered support and advice it kept me sane.

[Scott Larson]

CONGRATULATIONS!!! Good news indeed...Now, don't muck-about under the dash anymore! :thumbup: :_beer: :clap:

[Maddawg]

OK...This morning got deep into the wiring under the dash. Checked all of the connections moved wires around tightened up and cleaned everything I could find and........it started.

Not sure exactly what was loose but she is alive. :bgwb::clap:
It was most definitely a wiring or connector problem I just wish I knew exactly what I did.

Bunches of thanks to everyone who offered support and advice it kept me sane.

Did that fix your dash indicator lights as well??

[Triathlete]

I would check the wiring in the areas you moved around for any areas where it might have rubbed the wiring causing a short. Possible a grommet worked its way out or just didn't exist.

[bcbike]

Everything is functioning dash lights, fuel gauge and the code reader works. My best guess is it was a ground high on the left side kick panel that has about 4 wires going into one terminal. I noticed on the wiring diagram that it looked like the fuel gauge, tach and check engine light all shared a common ground. I back tracked until I found a ground that had multiple wires and polished it up. I went over the harness under the dash and didn't find any bare wires or chaffing. I can't be certain the ground was it but it seems like the likely culprit.

[Scott Larson]

That's a fine bit of detective work there "Holmes"...:cool!:

[tom4bren]

I'm glad it worked out for you ... just sorry that you bought a 'puter that you didn't need based on my recommendation.

[bcbike]

Nope Tom, everything pointed to the computer even the diagnostic charts in the shop manual. No worries.