V1 JS City Goblin - 2010 LS

[SliderR1]

Your wing mounts look great! Tell us more about the wing - which one is it? I see how you modified the stock uprights. The pieces that bolt to the wing - did those come with the wing or did you fab those?

 

[JSATX]

might be worth checking the sock on the fuel pump for debris/dirt. Also fuel filter...

I pulled the pump last night. For some reason there was a few aluminum shavings in there but that’s it. The filter is also new. There is a return regulator in the pump housing. It’s starting to sound like that is stuck open, if it can’t sense fuel returning to the tank from the fuel filter it keeps pumping.

 

[JSATX]

Your wing mounts look great! Tell us more about the wing - which one is it? I see how you modified the stock uprights. The pieces that bolt to the wing - did those come with the wing or did you fab those?

It’s an APR GTC wing and I absolutely love the way it looks.

I chopped up the DF mounts quite a bit but they ended up working well. The curved mounts that are actually bolted to the wing and the turnbuckle adjusters come with the wing.

With only one center brace it’s rock solid. Does not move at all in any direction.

 

[ctuinstra]

The wing does look cool!

Curious as to what you find out about the fuel pressure and misfire. Very odd how unstable the pressure is. I don't know if that is normal the way it swings around, but sure doesn't seem normal.

 

[JSATX]

I took the whole pump apart today. It’s simpler than I thought it would be.

Can someone please do a continuity test on their pump. It’s the last thing I want to check before I buy a new pump. The two terminals on the left side of the plug control the pump motor. I get almost no resistance when I ohm them out.

Why would there be no resistance between the positive and negative terminals of an electric motor? I’m no electrical engineer but this seems weird.

 

[PHerder]

Just went out and checked the same terminals on my pump... same result... ~ 0.5 ohms.

 

[JSATX]

Just went out and checked the same terminals on my pump... same result... ~ 0.5 ohms.

Thank you!

...now I’m doubly confused.

 

[ctuinstra]

That seems about right for the pump motor. That would be a 24a load.

 

[JSATX]

Also just replaced the fuel filter even though I knew that wouldn’t fix it.

Here’s the return valve. I was expecting some sort of solenoid or at least an electrically variable valve of some sort. But it’s not. It’s just a mechanical pressure relief valve with a ball bearing seal.

Meaning there’s no way for it not to release pressure. That valve is totally free of debris. I’m wondering now if I have a plug in the return line.

 

[Waterdriver]

When you swapped the coil pack did you swap the plug with it?

I had the same issue with my Audi TT. New plugs and less than 1k miles and got a misfire in one cylinder.
Diagnosed to a cylinder. Swapped coil packs, no change.
Swapped plugs and followed the plug.

Found that the ceramic surrounding the center electrode cracked, sliding up and down.

Researched the plugs and found that some brands and models are sensitive to boost. The plugs I installed were one of those listed.

 

[JSATX]

When you swapped the coil pack did you swap the plug with it?

I had the same issue with my Audi TT. New plugs and less than 1k miles and got a misfire in one cylinder.
Diagnosed to a cylinder. Swapped coil packs, no change.
Swapped plugs and followed the plug.

Found that the ceramic surrounding the center electrode cracked, sliding up and down.

Researched the plugs and found that some brands and models are sensitive to boost. The plugs I installed were one of those listed.

That’s interesting. I have a new set of plugs but I’ve heard that the fuel pressure issues can cause misfires. So I plan to focus on fuel pressure problem first. I bought nice NGK iridium plugs one step colder than stock. They’ll go in just as soon as I have a consistent 60psi at the rail.

Plugs or injectors. I’ll be really bummed if my brand new injectors are having issues

 

[Waterdriver]

Have you tried swapping the injector from cylinder #4 to another cylinder to see if the misfire follows? Like you said, it could be a bad injector, not fully seating when closed.
Did the plug look rich, wet or smell of fuel?

I was thinking, if your overall fuel pressure was off, that you'd have misfires in all cylinders.

Would the misfire disappear if you brought the RPM up? Or remain?

Sorry for all the questions.

 

[Briann1177]

Motors use the principal of inductance much like an electromagnet. If you wrap piece of wire around a nail and hook it up to a battery, you'll get an electromagnet. If you measure the resistance between the two ends, you'll get a short.

 

[JSATX]

Have you tried swapping the injector from cylinder #4 to another cylinder to see if the misfire follows? Like you said, it could be a bad injector, not fully seating when closed.
Did the plug look rich, wet or smell of fuel?

I was thinking, if your overall fuel pressure was off, that you'd have misfires in all cylinders.

Would the misfire disappear if you brought the RPM up? Or remain?

Sorry for all the questions.

I haven’t swapped the injectors just yet because my main concern is getting fuel pressure corrected.

Spark plug looked completely normal.

Misfires really only happen at idle, I haven’t noticed any while driving. And the straight pipe makes them very easy to hear

 

[JSATX]

Nothing really to report. Spent another couple hours screwing around with the fuel pump. Being covered in gas is really annoying.

It just doesn’t make sense. With the car running it’s sitting at a very consistent 90psi. I’ve cleaned everything in the pump. The mechanism is so simple I just can’t understand why it won’t bleed at a lower pressure. I’m about to cut the lines off and check for blockage because that’s the only part of the system that could possibly be causing this. Even though I already blew them out with an air compressor

 

[syntroniks]

You may be able to log fuel pump control (duty cycle) with your tuning software. Some ECUs vary the output level to control fuel pump pressure.
At idle, I'd expect to see a constant number as well as a constant rail pressure. Initially I would suspect an electrical problem, but that wouldn't necessarily go away off idle.

I wonder if you can compare calibrations between stock and the one you are running now.

 

[George]

What is the voltage at the pump when running? Have you tried another gauge?
Has a compression test been taken?

Brad

 

[JSATX]

You may be able to log fuel pump control (duty cycle) with your tuning software. Some ECUs vary the output level to control fuel pump pressure.
At idle, I'd expect to see a constant number as well as a constant rail pressure. Initially I would suspect an electrical problem, but that wouldn't necessarily go away off idle.

I wonder if you can compare calibrations between stock and the one you are running now.

I am comparing now. Some things are changed and some arent. Im going one by one and trying to learn what each parameter does.

The tuner swears its not the ECM and that only the return valve pictured can control pressure.

 

[JSATX]

What is the voltage at the pump when running? Have you tried another gauge?
Has a compression test been taken?

Brad

Gauge worked perfectly fine before the turbo, I know its high because it blew one of the fittings off. Have not done compression test, how could that affect fuel pressure?

 

[George]

Compression test will not effect fuel pressure but may effect the miss. If the alternator is overcharging the pump will run to fast crating excess pressure

Brad