how reliable are stock injectors?

1348 Views 21 Replies 5 Participants Last post by Grant, Nov 14, 2001

G

Discussion Starter · Nov 13, 2001

I've seen many posts saying that injectors with high milage will not flow good. to my understanding injector is pretty basic part and not something that'll melfunction easily. Has anyone heard or ever had experience with stock injectors going bad?

1 - 20 of 22 Posts

Grant

· #2 · Nov 13, 2001

They get dirty from crap in the fuel.

But if you don't fix your FPR problem it won't matter what kind of injectors you have in there. The ECU ajusts the a/f by ajusting the amount of time each injector is open. It wants a constant pressure difference between the fuel and air intering the cylinder. If that pressure difference begins to drop, less fuel will make it into the cylinder and you will run dangerously lean like you are now.

supra178

· #3 · Nov 13, 2001

Grant said:
They get dirty from crap in the fuel.

But if you don't fix your FPR problem it won't matter what kind of injectors you have in there. The ECU ajusts the a/f by ajusting the amount of time each injector is open. It wants a constant pressure difference between the fuel and air intering the cylinder. If that pressure difference begins to drop, less fuel will make it into the cylinder and you will run dangerously lean like you are now.

what do you mean they get dirty from crap in the fuel? in california the highest octane is 91 and that's what we pump here. Jonas installed new FPR and the pressure drops at higher RPM. so do you have any ideas?

Marcus Frost

· #4 · Nov 13, 2001

Jonas's car has a lot of miles... over 100k I believe. Injectors do get dirty as Grant said from crap in fuel... fuel is not mineral water, it contains impurities which can, over time, clog an injector.

Injectors can also fail completely, although this is not very common.

However a clogged injector shouldn't cause a drop in fuel pressure, if you changed your FPS and still are noticing a drop in fuel pressure, there may be an issue with your pump. Have you done the 12v mod?

BTW, the "Supra GOD" title above your avatar is a bit egotistical for someone with a simple BPU 100k mile Supra, don't you think? Just a thought.

-m

Grant

· #5 · Nov 13, 2001

I think he has some sort of aftermarket FPR on the stock rail, thats probably whats been causing the problem.

Marcus Frost

· #6 · Nov 13, 2001

Grant said:
I think he has some sort of aftermarket FPR on the stock rail, thats probably whats been causing the problem.

I don't know about that... all FPRs are basically (keyword: basically) the same, and he had this problem on his stock one as well as with his new HKS one.

-m

G

Discussion Starter · #7 · Nov 13, 2001

I put in HKS FPR cuz I didnt wanna go thru the trouble of taking out stock FPR and replace it...plus, the HKS FPR might come for handy in future upgrades. There is no aftermarket FPR that replaces stock FPR directly. plus, with high milage on my car, its good idea to replace parts whenever I havean excuse. thats why I've replaced almost everything on the fuel system...except for injectors.
as I said, I replaced the vacuum hoses that goes from stock FPR to the solenoid on the intake manifold, so I'm gonna test drive the car and see if thats the problem...cuz my symptom is beginning to sound like a pressure leak.

"Supra GOd" is just for fun, nothing egotistic about it

I love supras and I've been on this forum for a while now, dont take it personally. you can be one too

I wanna learn more about the characteristics of injectors, FPR, and dampener...anyone wanna give me a basic lessons here?

Marcus Frost

· #8 · Nov 13, 2001

So wait, you have 2 FPRs? Even if your HKS one is working properly, if you still have your stock one after the HKS and it is cutting back pressure before the fuel hits your rail, you're still going to be losing pressure. Don't be lazy - running lean is asking for a lot of trouble.

I was also going to suggest a leak in your lines... how much pressure are you losing? I also asked you various other questions which you didn't answer (12v, if you are losing pressure under boost or whatnot)...

In regard to being offended by the "Supra GOD" thing... not at all, I don't care, but whether or not you think it's egotistical, in reality it is... even for someone with a fast supra or someone who knows a lot about them it would be... it's just an FYI...

-m

BLKMGK

· #9 · Nov 13, 2001

losing pressure...

If he's got two regulators inline with one another thenwhichver one is set to a higher pressure is the one that will take over. IF his stock unit is ahead of th enew one and allows more fuel to flow out th ereturn the second one will see the lower pressure and lower the return flow - bumping pressure.

The only issue I can see with doing this, in a generic EFI sense, is that the "return" line to the tank from the first regulator, which wouldn't normally see much pressure will probably be seeing as much pressure as the second unit is set for.

I'm not positive this would be "bad" but it's probably not real good.

How exactly is the new regulator setup, is the original one still installed, and if so which one has the vac line connected to it? Why is the pump not a suspect? I'd be checking feed voltage to the pump and it's health, especially with 100K on the clock - is this a replacement pump?

Dunno' much about Supras I'll admit but I DO understand EFI and the attendant plumbing....

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Marcus Frost

· #10 · Nov 13, 2001

My mistake...

I meant, if the HKS one is BEFORE the stock one, and the stock one is still cutting back pressure, then you aren't going to get anywhere, but as you said BLK, that depends on how much pressure it is cutting back for... the HKS one should be able to make up for it.

You make an interesting point about return lines also, how do you have yours setup Jonas?

-m

G

Discussion Starter · #11 · Nov 13, 2001

I want to know how you got a non-stock regulator on the stock fuel rail. I have borrow a friend's fuel rail/injectors/regulator to investigate the use of a upgraded fuel presure regulator, and didn't see a way to do it without removing the rail, removing the injectors, and doing some welding to replace the stock regulator with a -6AN connection to run to a aftermarket regulator.

G

Discussion Starter · #12 · Nov 14, 2001 (Edited)

ok, my HKS FRP is placed after stock FPR which basically bypasses stock FPR and takes over control of the system. THe vacuum line is T'ed into the stock FPR vacuum. Not sure how the fuel lines run, Bruce Nomura did the installation for me so I 'm pretty sure its set-up correctly. I see 2 fuel lines coming out of my HKS FPR, 1 connects to a metal line located underneath the intake manifold..near the oil dipstick, and I think another line connects to the fuel filter. Not sure which line is the return line though...
BLKMGK, I replaced my old fuel pump with a new stock pump already.

AZWildcat

· #13 · Nov 14, 2001

Some good info in this thread..

I have come in late on this problem, so I'm sure there's some thread where the problem is detailed more. Any links?

Marcus Frost

· #14 · Nov 14, 2001

Dennis,

I have been trying to piece together the whole picture from Jonas but information seems to be difficult to get out of him.

Basically, he has a fuel pressure gauge which is indicating a drop in pressure in higher rpms (and I am assuming under high boost - *I think* he is running TTC). He tried adding an HKS FPR to aleviate the problem (in addition to his stock FPR) but it has been to no avail. He does not have the 12v mod and is running a BCC that he tuned by taking his car out and hitting fuel cut then adjusting the screw (not with a voltmeter) until he didn't hit it.

I suspect either he turned the screw enough on the BCC to indicate a vacuum signal on the turbo pressure sensor, causing the car never to switch the fuel pump from 9v to 12v mode, or he wired his BCC improperly and it's feeding the ECU no signal at all (ie, running as if it was a FFCD).

-m

AZWildcat

· #15 · Nov 14, 2001

Marcus,

Marcus Frost said:
Dennis,

Basically, he has a fuel pressure gauge which is indicating a drop in pressure in higher rpms (and I am assuming under high boost - *I think* he is running TTC).

This is a pretty key part.. by going down, do you mean it goes from stock pressure (isn't it 38? I don't remember) and falls under boost, or the fuel pressure doesn't raise a 1:1 with boost?

He tried adding an HKS FPR to aleviate the problem (in addition to his stock FPR) but it has been to no avail.

In my experience, the FPR is always the first thing people go to, and 9 times out of 10 the wrong thing.

He does not have the 12v mod and is running a BCC that he tuned by taking his car out and hitting fuel cut then adjusting the screw (not with a voltmeter) until he didn't hit it.

I suspect either he turned the screw enough on the BCC to indicate a vacuum signal on the turbo pressure sensor, causing the car never to switch the fuel pump from 9v to 12v mode, or he wired his BCC improperly and it's feeding the ECU no signal at all (ie, running as if it was a FFCD).

There isn't wrong with adjusting the BCC like that so long as it's in small incriments. (e.g. turn it until it cuts, and then make small adjustments until it doesn't) Through the BCC's design, it's very unlikely it's showing vacuum. I used to know the voltage to pressure scale, but the BCC would have to cap voltage at ~2V for that to be the case. The BCC is a series of opamps designed to allow voltage to pass uninterrupted until the feedback loop of one op amp reaches the input of the signal, at which point the feedback loop becomes output.

Let's assume however the pump never goes to 12V.. the pump should still be flowing enough at 9V to up the pressure. I seriously doubt if 38 PSI (or whatever stock pressure is) just happens to be the limit at 9V.

As far as fuel leaks, I have had MASSIVE fuel leaks where the car maintained pressure and increased with boost. If there is no smell of gas, I suspect one of the hoses in the tank has gone bad and that's where the leak is.

Take out the pump and examine the lines. Or just replace them for good measure.

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G

Discussion Starter · #16 · Nov 14, 2001

Marcus Frost said:
Dennis,

I have been trying to piece together the whole picture from Jonas but information seems to be difficult to get out of him.

Basically, he has a fuel pressure gauge which is indicating a drop in pressure in higher rpms (and I am assuming under high boost - *I think* he is running TTC). He tried adding an HKS FPR to aleviate the problem (in addition to his stock FPR) but it has been to no avail. He does not have the 12v mod and is running a BCC that he tuned by taking his car out and hitting fuel cut then adjusting the screw (not with a voltmeter) until he didn't hit it.

I suspect either he turned the screw enough on the BCC to indicate a vacuum signal on the turbo pressure sensor, causing the car never to switch the fuel pump from 9v to 12v mode, or he wired his BCC improperly and it's feeding the ECU no signal at all (ie, running as if it was a FFCD).

-m

My fuel gauge reads 2.2 bar at idle, 3.0 at 0 PSI which is dead on with stock spec. as I go full boost, I am now about 3-4 psi short.
I am runing TTC, did the 12V mode and tuned BCC to 4.3 V tonight(I wasnt too far off at 3.9V). havnt got the chance to test the car yet. will post result once the road dries up.

AZwildcat, I dont think getting an aftermarket FPR is the wrong mode to get, it helps me to fine tune my FP incase my stock FPR is going bad. plus, it would be helpful later on when I upgrade turbo.

I have discussed my problem with Bruce Nomura, and we came to conclusion that if the fuel pump never switched to 12V and stuck in 9V, the overhating problem would appear alot sooner than 5th gear top end pull. I would be running really really lean even at lower gears and have really high EGT in all gears.
I will open up my fuel tank and examine the fuel lines again...cuz I dont smell fuel.

thanx for you guys help.

Jonas

AZWildcat

· #17 · Nov 14, 2001

Zerosoul said:
My fuel gauge reads 2.2 bar at idle, 3.0 at 0 PSI which is dead on with stock spec. as I go full boost, I am now about 3-4 psi short.

What does 3-4 PSI short mean? I see what you mean Marcus, it is hard to get info.

This is not a 9-12v switching problem, please check your pump lines.

G

Discussion Starter · #18 · Nov 14, 2001 (Edited)

3-4 psi short at full boost meaning when I am at full boost, my fuel pressure supposed to be about 4.3 bar, but instead, I am at about 4.0 bar. for every psi of boost gained from the turbo should gain a psi with fuel pressure. Therefore, if I boost 1.3bar, I should gain 1.2 bar on fuel pressure, which means at full boost I should be geting 3.0+1.2= 4.3 bar.

which fuel lines are you talking about? check and see if its leaking? there is no way I can find out if its clogged inside the line, the only lines I can replace are the rubber hoses that connects to top of fuel pump. plus, I dont smell gas anywhere in the engine and around the fuel pump/trunk area.

thanx

Jonas

AZWildcat

· #19 · Nov 14, 2001

Zerosoul said:
3-4 psi short at full boost meaning when I am at full boost, my fuel pressure supposed to be about 4.3 bar, but instead, I am at about 4.0 bar. for every psi of boost gained from the turbo should gain a psi with fuel pressure. Therefore, if I boost 1.3bar, I should gain 1.2 bar on fuel pressure, which means at full boost I should be geting 3.0+1.2= 4.3 bar.

I don't think I'd even be worried about this. This also takes away from my gas tank theory (for reasons I can go into, but you're probably not interested), but it should still be checked. Very easy to do.

the only lines I can replace are the rubber hoses that connects to top of fuel pump. plus, I dont smell gas anywhere in the engine and around the fuel pump/trunk area.

Click to expand...

Lines inside the tank.

G

Discussion Starter · #20 · Nov 14, 2001

Lines inside the tank...sounds like fun! will check that first thing in the monring.
BTw, is there anything specific I should look for?

thanx Dennis

Jonas

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