Fuel Pump or Wiring?
08-15-09, 06:51 AM
#1
Crispy Beef
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Fuel Pump or Wiring?
Hi Guys,
For whatever reason I cannot get my FD to fire. First I had a listen to see if I could hear the fuel pump coming on when I switch the ignition ... nothing. So I thought it might be a blown fuse, broken/incorrectly seated relay. Went through the obvious places and all fuses and relays are just fine as far as I can tell. Next I had to think about if the actual pump was broken, so I bridged to points in the diagnostic module to see if the pump would operate, this time it did, I can hear it humming away nicely. So this leads me to believe that I might have a bad ground on the fuel pump wiring in the back.
I took off the cover and removed the wires, and tested with the ignition on, I'm getting the same voltage through the normal fuel pump wiring that I would expect, also tested with a different ground and get the same results. After looking over the workshop manuals I cannot see anything else that would affect the fuel pump from starting when the ignition key is turned. Is there something that I'm missing in the ignition wiring?
I should also mention that when I bridged the gap with the diagnostic module and turned the engine over I could smell the fuel, so I think the pump is good, just some wiring somewhere?
Any thoughts or ideas on where to look next would be most appreciated.
For whatever reason I cannot get my FD to fire. First I had a listen to see if I could hear the fuel pump coming on when I switch the ignition ... nothing. So I thought it might be a blown fuse, broken/incorrectly seated relay. Went through the obvious places and all fuses and relays are just fine as far as I can tell. Next I had to think about if the actual pump was broken, so I bridged to points in the diagnostic module to see if the pump would operate, this time it did, I can hear it humming away nicely. So this leads me to believe that I might have a bad ground on the fuel pump wiring in the back.
I took off the cover and removed the wires, and tested with the ignition on, I'm getting the same voltage through the normal fuel pump wiring that I would expect, also tested with a different ground and get the same results. After looking over the workshop manuals I cannot see anything else that would affect the fuel pump from starting when the ignition key is turned. Is there something that I'm missing in the ignition wiring?
I should also mention that when I bridged the gap with the diagnostic module and turned the engine over I could smell the fuel, so I think the pump is good, just some wiring somewhere?
Any thoughts or ideas on where to look next would be most appreciated.
08-15-09, 08:36 AM
#2
with the diagnostic connector jumpered, can you hear the pump running with the key in the ON position, engine off? it should run continuously as long as the ignition is on and the main relay active. The diagnostic connector is constantly supplying the ground to the fuel pump relay that the ECU would normally supply based on its control logic. The main relay supplies the +12V side for the coil in the fuel pump relay.
if the pump is running continuously, and fuel pressure is good (maybe 37psi on stock regulator with the engine off?), it's not a fuel pump issue that is directly keeping the engine from starting. Now there may be some fuel pump control related issue (resistor relay, whatever) but that should be unrelated. If you get the car running with the fuel pump diagnostic connector but it gets no fuel pressure without it, then you've got something wrong with the ground signal for the fuel pump relay (which the ECU normally supplies).
do you have spark? is the car flooded? what led up to this anyway, did it just die on you one day or were you doing some modifications?
if the pump is running continuously, and fuel pressure is good (maybe 37psi on stock regulator with the engine off?), it's not a fuel pump issue that is directly keeping the engine from starting. Now there may be some fuel pump control related issue (resistor relay, whatever) but that should be unrelated. If you get the car running with the fuel pump diagnostic connector but it gets no fuel pressure without it, then you've got something wrong with the ground signal for the fuel pump relay (which the ECU normally supplies).
do you have spark? is the car flooded? what led up to this anyway, did it just die on you one day or were you doing some modifications?
08-15-09, 08:52 AM
#3
Crispy Beef
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hi arghx
Thanks for the reply.
Yes the fuel pump is running continusously when the diagnostic module is jumpered. The car has been off the road for a while due to financial constraints but now I'm putting it back on the road. Last time I tried starting it it fired perfectly, I've been away for a few weeks and this time it didn't want to start. It has a new fully charged battery, half a tank of fuel. As far as I know it's not flooded, I tried starting it with using the "deflooding techique" just in case, but no go. The fuel pump just doesn't want to come on from the ignition switch.
I will admit that I haven't yet tried starting properly with the diagnostic module jumpered as I wasn't sure if that would cause problems. But I will try that first thing on Monday morning.
Not sure how to test for fuel pressure as I don't have the required equipment. I'll do some research on that now.
Thanks.
Thanks for the reply.
Yes the fuel pump is running continusously when the diagnostic module is jumpered. The car has been off the road for a while due to financial constraints but now I'm putting it back on the road. Last time I tried starting it it fired perfectly, I've been away for a few weeks and this time it didn't want to start. It has a new fully charged battery, half a tank of fuel. As far as I know it's not flooded, I tried starting it with using the "deflooding techique" just in case, but no go. The fuel pump just doesn't want to come on from the ignition switch.
I will admit that I haven't yet tried starting properly with the diagnostic module jumpered as I wasn't sure if that would cause problems. But I will try that first thing on Monday morning.
Not sure how to test for fuel pressure as I don't have the required equipment. I'll do some research on that now.
Thanks.
08-15-09, 10:17 PM
#5
remove at least one of the sparkplugs and check to see if they are soaked in gas. I've probably had at least 50 floods in my day, 2nd gens are notorious for them. A bad flood can't always be cleared by just cranking the engine over. sometimes pushing it and popping the clutch is the answer.
08-17-09, 03:37 AM
#6
Crispy Beef
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I've had to un-flood it in the past by removing the sparks so if I get no joy after trying with the fuel pump jumpered will take out the sparks, have some time at lunch today so will give it a go then...
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10-09-09, 05:03 PM
#14
Shinji
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you might want to make a new wiring loom or solder the pins from your ECU - make sure all wires are properly connected and all the electrical joins are solid. if your wiring was replaced, or if you know your wirings are in good condition, don't worry about this part..the fuel-pump relay is not controlled by the ECU anyway. install a new relay and replace the fuel-pump wiring. check your fuses. do not use the output of the pfc because fuel-pump relay will not work! if all goes unsatisfactory, work your way to the igniter.
10-10-09, 04:24 PM
#16
ok so here is the update.
I removed the circuit relay and jumped the pins, I finally recieved 6.5V to the pump. But my fuel pressure regulator only states a 30~psi at the rails. I assume this basically answers my question that the circuit relay is no good. But here is what gets really interesting...I have spark at the plugs and now have fuel but the car doesn't want to start....what else could be wrong....
I removed the circuit relay and jumped the pins, I finally recieved 6.5V to the pump. But my fuel pressure regulator only states a 30~psi at the rails. I assume this basically answers my question that the circuit relay is no good. But here is what gets really interesting...I have spark at the plugs and now have fuel but the car doesn't want to start....what else could be wrong....
10-10-09, 04:41 PM
#17
Have you gone through the deflood procedure including putting some ATF fluid in the chambers to build compression?
As for the wiring you could always find a wire that is switched with the key on and activate the relay, or run a new relay with that wire. The only problem with that, is then the fuel pump will run the whole time the key is on. Not really an issue unless you like to listen to the radio or something with the key on and car off, then the battery would go dead faster. I suppose along those same lines you could hook the diagnostic connector up constantly. Or hook a switch up. The fuel pump runs once the engine is started so the only difference is when the engine isn't started.
As for the wiring you could always find a wire that is switched with the key on and activate the relay, or run a new relay with that wire. The only problem with that, is then the fuel pump will run the whole time the key is on. Not really an issue unless you like to listen to the radio or something with the key on and car off, then the battery would go dead faster. I suppose along those same lines you could hook the diagnostic connector up constantly. Or hook a switch up. The fuel pump runs once the engine is started so the only difference is when the engine isn't started.
10-10-09, 04:50 PM
#18
I was thinking about going through the de-flooding procedures.....while my battery is charging....but I hope that would be it...I am thinking about running a seperate switch to the fuel pump so I can also increase the voltage to 12V to the pump and get the 40psi I am seeking...but is it normal to have 6.5V or so at the pump when the key is in the on postition? Does my fuel pressure sound right?
I am going to look for a new relay so I don;t have to have my circuit relay jumped...
well I guess i will deflood and throw in some ATF fluid...doesn't hurt i guess...
I am going to look for a new relay so I don;t have to have my circuit relay jumped...
well I guess i will deflood and throw in some ATF fluid...doesn't hurt i guess...
10-10-09, 05:00 PM
#19
You should have closer to 40 psi with the car off. But thats not why the car isnt starting. And i think you should have more voltage at the pump. The fd resistor packs reduce the voltage to around 9 i think, and then give a hopefull 12 under boost. Not sure how the 2nd gens are setup. I personally bypass the resitor and run a 10g wire to the pump and use the old fp wire to activate a relay.
10-10-09, 05:51 PM
#20
oh, I have a 94 3rd gen. So I went ahead with the de-flood and ATF route, cleaned the plugs and still no go...I just dont get it. I even ran a wire directly to the fuel pump from the battery to instantly give it the 12V and the regulator then reads 40psi. But if I only jump the circuit relay I only get 6.5V to the pump...I am very stumped with this setup....unsure why the car won't start....I have tried just about everything imaginable...
10-11-09, 10:29 AM
#25
Shinji
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use the fd igniter, because this igniter has no tachometer output (on trailing coils). solder the 2b signal from powerFC into tachometer input on the FC harness (yellow with blue stripe wire on the trailing coil pack wiring). do not use the FC iginiter because there will be no spark at rear trailing plug - as there is no 1V select signal from the ECU to control the spark on the second trailing spark, only front trailing spark will fire but not the rear one. and tachometer will read half the real rpm value. so use the FD igniter.
it's your wires, just re-check them.
it's your wires, just re-check them.