Do we have a post detailing exactly how to perform a fuel pressure test on a tpi vehicle ?
If so I can't find it and would appreciate any help from forum members who know. I believe I know the basics, depresurise the fuel system, (is removing the fuel cap ok for this ?)
hook up gauge via Schrader valve, turn key to on so the pump primes and pressure should rise to around 40psi and should remain at this pressure for around half an hour till it stars to drop?

I'm going to be checking to see if I have leaking injectors to try solve my excessive fuel consumption, hard starting after first initial start of the day, fuel smell under hood (not raw fuel just strong odor), fuel smelling exhaust and general excessive carbon build up in plenum/ runners/ throttle body and exhaust.

I've had the original factory injectors serviced a year ago but the problem was around before and after that, they wouldn't touch the cold start one out of fear of breaking it, fuel pump is new, fuel pressure regulator is new, filter new and I've inspected all the fuel lines for leaks and all check out ok. I am suspecting the cold start injector is leaking. Thanks for any and all advice.

 

The Schrader valve is on the passenger side fuel rail towards the firewall. Just screw the gauge on it as fast as you can, keep a rag nearby and you'll only need to catch a dribble. I had difficulty getting the fuel pump to prime at full psi, but running the engine for 10 seconds should do it. Yes, it should maintain pressure if everything is sealed correctly, it might drop 1-3 psi after half an hour but should mostly maintain the pressure.

 

Thanks Komet.
I went ahead and just did what I thought was right.
Hooked up the gauge then turned the key to run and the pump primes and it goes up to 40 psi but immediately starts to drop. Bad sign.
Started the car and it idles at 30psi and just under.
While its running I disconnected the vacuum line to the regular, I have vacuum which is good lol and the gauge jumped up and maintained 40psi, plug vac line back in and drops back down to 28-30psi. Turned the car off and in under 2 mins the pressure is 0.
Where does one go from here ? Like I've mentioned I at least suspect the cold start injector is leaking but maybe even after servicing the old ones are still junk. They're a bit pricey for me to buy just to eliminate but it seems to me like they're the culprits.

 

Pull the cold start injector out but leave the hard line attached. Put a rag underneath it, and prime the fuel system. Does it leak?

 

I'll check that next.
To help me understand, should the cold start injector only spray while the pump primes then shut off ?

 

A rapid drop in pressure after the pump shuts off is not ideal, but it also isn't necessarily a major problem. If the bleed off of fuel pressure is due to the regulator slightly leaking back to the tank or the pump check valve bleeding off pressure, the system could operate without any problems almost indefinitely. If an injector is leaking or there is an external leak, that could be a problem.

It's not a big problem to program the cold start injector out of the system either.

 

Vader, I have very high fuel consumption (I may have forgotten to mention, among other things like excess carbon build up, slight misfire and hesitation accelerating) which has slowly been getting worse, I'm lucky to get 170 miles from a ful tank so I'm really of the opinion it's a leaking injector, if it were the regulator or check valve I'd not be experiencing the high fuel use is that correct ?
I've read about deleting the csi, will that just give me a longer crank when cold ? No other issues ?

 

The 9th injector can be removed, and the appropriate way to do that is to enable cold start enrichment in the programming so the service injectors perform the necessary function.

 

So I tried this, pulled the csi and primed, no fuel comes out at all, bone dry. Does this mean I have a good csi ?

 

That's the result I would expect if the csi was good / not leaking.

Considering the rest of your system is new, and OE injectors are known to be problematic, I would now be suspicious of leaky injectors. Or, your new fpr is defective, but that doesn't seem to add up with the gas smell, etc.

When you prime the fuel system, does the fuel smell get more noticeable as the pressure bleeds off?

 

That's good and bad lol, still have to find the problem!

OE injectors but were serviced not long ago, same problem persists before and after that but I'd have thought they'd tell me that 1 or more were leaking or not working well ? No way to tell I guess unless I pull the whole rail and check 😫, probably time to replace with new ones anyway. I would have thought if it were the fpr, it would've shown in the test I did ? Removed the vac line and pressure rised, dropped back down when reinstalled the vac line, does that not show the fpr is operating fine ?


No different, it's not a very strong raw fuel smell, more of just an odor..

 

Might be useful to pinpoint the strongest source of the smell. I'd reckon leaky injectors would cause fuel smell in the plenum if you open the throttle blades and jam your nose in there. Another possibility would be a failure of the evap system.

 

Would a failure of the evap system have anything to do with consumption ?
Tbh at this point I wouldn't rule out its failure.
I'm leaning towards the injectors too, but would you you say there isn't much left aside from them to draw a conclusion ?

 

Not really. My thinking here is it could be the cause of the fuel smell and the consumption is unrelated.It seems to me like either the injectors are leaking or the fpr is letting an abnormal amount of fuel back to the tank (but a leaky fpr wouldn't explain the fuel smell). Or you've got a physical leak somewhere.

In terms of more troubleshooting, I suppose a datalog and/or checking the plugs could be beneficial.

 

Yes those damn plugs, got to love taking them out on these cars. I'll check that on my next day off.
I definitely cannot find any leaks anywhere on the car, the exhaust smells very rich too so I'm really leaning towards the injectors.
Do you think the coolant sensor for the csi could be faulty, something along the lines of it thinking the car is always cold and keeps the csi going or something ??
I'll get the plugs out and photograph each and post for opinions. Thanks for the help man.

 

Hi Vader, where can/ who can program in the cold start enrichment?

 

Get ahold of Tuned Performance on here, he took care of mine and did a basic tune as well. After the new PROM/chip the car runs cooler, starts faster and is more responsive than before. To delete the CS inj. you can get a kit for like $30 on ebay and its pretty simple to do especially if done while replacing injectors.

His website is www.tunedperformance.org

 

Thanks reddragon, just what I needed.

 

Just had this problem sneak up on me,...... Bad fuel pump.

(ECM plugged in, Injector fuses installed)

Installed a FP gauge: Turn key to RUN & the pump would build 40LB,... then it would quickly drop to 0.

Pinched the return line: Turn key to RUN & the pump would build 40LB,... then it would quickly drop to 0. ( can't be the return )

Pinched the return line + unplugged ECM & removed injector fuses: Turn key to RUN & the pump would build 40LB,... then it would quickly drop to 0. ( can't be the return & probably not the injectors, what's left ?)

**WITH HELPER: Pinched the return line + unplugged ECM & removed injector fuses, Turn key to RUN & the pump would build 40LB; HAVE HELPER PINCH MAIN FUEL LINE... Pressure holds.

**WITH HELPER: Un-pinch return line, Un-pinch main fuel line, plug in ECM, install Injector fuses, Turn key to RUN & the pump would build 40LB; HAVE HELPER PINCH MAIN FUEL LINE... Pressure holds

Check valve in the fuel pump failed.


I've also found a bad ECM in this way before........ Pressure would drop pretty quick after building the 40lb during prime.

ECM plugged in, Injector fuses plugged in, ALL injectors disconnected. Pinch return line and main line( with helper after pump prime), Turn key,... pressure holds.

Leaving key in RUN, now connect one injector, pressure begins to drop. Disconnect that injector, pressure holds. Plug in a different injector, pressure begins to drop. Disconnect that injector, pressure holds. Method can be used to check for a single injector sticking open and to check if all are leaking; if all are leaking then suspect the ECM.

 

Thanks I'll give this a try. I'm eliminating the pump as my problem because I'm definitely going through the fuel bigtime and the consumption is getting worse.

 

What about a bad O2 sensor, causing it to run pig rich which would give you the bad fuel consumption and fuel smelling exhaust along with the carbon build up?

 

if you had a leaking injector, id think it would be running really bad? that and your initial start might be hard too since it'd be leaking fuel after shut off...and your oil would probably smell strongly of gas.



try change the coolant temp sensor for the ECM. Its right in front of the intake manifold. it could be sending a bad signal to the ECM. I had this issue in my S10 and old Camry.


.

 

Both o2 sensor and coolant temp sensor are new, no change with the new ones compared to the old.

The exhaust does smell super rich, I just kind of eliminated the o2 and temp sensors cause it is the same deal with the old and new ones.

Initial start is good if left overnight but any other start is hard but I agree that you'd think it'd be running pretty rough with such excess fuel.

 

Just a little update on this thread for future reference for those with similar issues...

I did/do in fact have two leaking injectors.
I removed the fuel rail and primed the system and two continued to drip fuel after priming.
In the coming weeks I will be installing bosch 3's from Southbay along with a new Tuned Performance chip deleting the cold start and will report back.

 

ahhh this should be interesting!!


You gonna block off the CSI?

 

Yep! Got the injectors, the new tune and csi block off kit all on my bench awaiting install!
Ditching that csi before it inevitably screws me around lol