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The part number in red is the resistor, worth a check. It sits on the bracket below the air pump on the passenger side. I don't really think the fuel pressure drop is the issue.
Do you have any logs that show your coolant temps? I am not sure how sensitive the ECU is but if the ECT is giving the ECU temps that are hotter than what it actually is then I can see how it would cause a lean issue.
The ECT is on the back of the thermostat housing and looks like this:
I got mine at a local autoparts store.
i think this pic is a four port but you get the idea.
Yeah I would just want to see it in a log to see if there are any weird fluctuations that you may not be noticing. Or you could just test the sensor as well.
Easiest thing to do is take the resistor out and just jump the wires together at the connector. This will force the fuel pump to run full speed mode under all conditions
Doing some test runs when I floor it I am definitely seeing an approx. 2-3psi dip in fuel pressure for that 1 second or so after I go WOT; after which it climbs back up to about 53-54psi and holds till redline. So I've tested the voltage across my fuel pump, see pic below of where I tested it.
I am seeing 10.5V to the pump no matter what RPM I'm at, revved from idle to redline and it held strong between 10.35 and 10.55 Volts never kicking up to a higher voltage. I only had a second to deal with this as I was away on vacation and now I'm back at work for a week. Next steps will be to replace my fuel pump relay and check any relevant fuses. From what I see there are two relays, a fuel pump relay and a fuel pump speed control relay. I can only assume the fuel speed control relay is the one bypassing the resistor?
Does anyone know what voltage the pump should be seeing at idle? Is 10.5V low? Reason I ask is that maybe my fuel pump resistor is shot as well explaining my relatively low fuel pressure.... Idle around 55-56psi, less pressure with more heat.
Doing some test runs when I floor it I am definitely seeing an approx. 2-3psi dip in fuel pressure for that 1 second or so after I go WOT; after which it climbs back up to about 53-54psi and holds till redline. So I've tested the voltage across my fuel pump, see pic below of where I tested it.
I am seeing 10.5V to the pump no matter what RPM I'm at, revved from idle to redline and it held strong between 10.35 and 10.55 Volts never kicking up to a higher voltage. I only had a second to deal with this as I was away on vacation and now I'm back at work for a week. Next steps will be to replace my fuel pump relay and check any relevant fuses. From what I see there are two relays, a fuel pump relay and a fuel pump speed control relay. I can only assume the fuel speed control relay is the one bypassing the resistor?
Does anyone know what voltage the pump should be seeing at idle? Is 10.5V low? Reason I ask is that maybe my fuel pump resistor is shot as well explaining my relatively low fuel pressure.... Idle around 55-56psi, less pressure with more heat.
You should do what Team suggested above and see if it fixes the issue .
may be a bad relay, the default wiring path is the lower voltage resistor mode until the speed control relay (far upper right in the diagram) closes and allows full voltage to bypass the resistor. You can jumper it at the fuse box contacts too by pulling that relay.
may be a bad relay, the default wiring path is the lower voltage resistor mode until the speed control relay (far upper right in the diagram) closes and allows full voltage to bypass the resistor. You can jumper it at the fuse box contacts too by pulling that relay.
Thanks Team! So you're saying that by pulling the fuel pump speed control relay it should bypass the resistor? Or I need to pull the relay and jump the wires going to that relay?
that
or you could put a known good relay in there too ...like i suggested the other day .
you can do this any number of ways ........... pick one
Understood haha, just wasn't sure if he meant that circuit would fail closed if the relay was removed (which I know wouldn't make sense by looking at the wiring diagram).
New relay's will be my first attempt to fix this (and inspect fuses), if that fails I will cut the resistor wiring to the harness and bypass the resistor completely.
Last edited by RotaryMachineRx; 07-10-2015 at 08:00 AM.
You just pull the relay and jumper the two relay terminals in the fuse box to simulate a closed relay switch. All you need is a short piece of wire with both ends bare and stick it in there.
But sounds more like you need someone who has basic electrical knowledge to assist you.
How old is the wideband sensor? Slow response is a symptom of a failing sensor.
It is the original stock sensor AFAIK. I don't notice any delay when letting off the gas though, goes straight to 20+ AFR. Also my AEM wideband in the Midpipe is reading the same delay as my stock wideband in the downpipe. Definitely worth a try if the relay doesn't solve my problems though.
It's possible that revving the engine only won't result in the PCM activating the high speed mode. Once you make the relay jumper and see high voltage at the pump, then you need to make a run and see if that resolves the problem or not. If not, you'll need to keep looking.
A second O2 sensor showing the same results eliminates it being that. No way would they read the same otherwise.
It's possible that revving the engine only won't result in the PCM activating the high speed mode. Once you make the relay jumper and see high voltage at the pump, then you need to make a run and see if that resolves the problem or not. If not, you'll need to keep looking.
A second O2 sensor showing the same results eliminates it being that. No way would they read the same otherwise.
It is load based up to high 3000s rpm then will switch over to high speed regardless of load .
So jumping the speed control relay resulted in my fuel pressure bumping up to 60psi at idle, great! But when I went out for a WOT pull my fuel pressure dropped back down from 60psi to 52ish psi again. There is is an obvious problem somewhere and I am just waiting for the fuel pump tool I ordered from Charles to show up so I can have a look at the assembly.
I bought new relays (fuel pump and fuel speed control relay) and replaced the old ones. After doing this my idle fuel pressure when back down to 56-57psi and my voltage at my fuel pump did not change with any rpm variance again. With the relays in I am seeing 10.55v across the entire RPM band; when I had the relay jumped I was seeing 13.5v to the pump.
I don't know what to do next in regards to the Hi/Low pump stage, need to find a good auto electrician to go over the whole system maybe.... and hopefully I can find something simple when I pull the fuel pump assembly in regards to the fuel pressure drop (maybe pop off valve isn't sealed shut correctly?).
06-26-2015, 04:29 PM
I am just thinking of all the things that can cause lean issues.
