Fuel Injector Woes

2543 Views 29 Replies 13 Participants Last post by Tyther, 1 mo ago

Tyther

Discussion Starter · 6 mo ago

I have 180k on my 1995 Roadmaster and I am having injector issues. It started about a month ago I started having difficult cold starts. I replaced the fuel pump earlier in the spring with a Racetronix. I did a pressure test and found the pressure gets to between 40-45 and starts to drop. The system looses pressure <2 minutes. Does anyone know if these Racetronix pumps have a check valve? When I initially replaced the pump I was not having issues. It was only after I put about 2000 miles on it when something started to seem off. I removed the fuel injectors and then cleaned them with pressurized carb cleaner. After flushing and back flushing, I put each injector in an ultrasonic cleaner with Seafoam for 10 minutes while actuating the injector with a pulse generator. I put everything back together and now the car went from hard starts, to flooding at starts and running with a miss.

My next idea is to remove the fuel rail again and prime the pump and check each injector for leaks. They were leaking before I cleaned them during this test but I did not re-test before I reassembled (cocky I fixed it). I have read in previous post people going to Cruzin Performance for injector cleaning services and I sent Rich an email. I described the situation and he claimed that the original Multec injectors have reached the end of service life and I would be better off sourcing new ones. If the the original injectors on these cars are reaching the end of life then the other LT1 cars must be toward the end of the road as well. It seems more common on the other forums people injectors are starting to give up.

So now what? AC Delco injectors are $80-$100 per injector. I like my Roadmaster for sure, but itself is reaching end of service life. Living in the rust belt does not help...

I have heard good reviews from this site and others on the ACCEL injectors but again, this is $400! Anyone had good luck finding a cheaper source?

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Marky Dissod

· #2 · 6 mo ago

1. Did you mention the fuel pressure regulator?
2. When firing the parts cannon, start with the lower caliber ammo (cheaper parts / labor) first.
3. Gotta replace injectors? OE mid 90s injectors corrode in the presence of E10; they WILL die.
Upgrading to E85-capable injectors for a 6.0L or 6.2L V8 is worth every penny.
4.

Tyther said:
I like my Roadmaster for sure, but itself is reaching end of service life.

Sell it to one of us, then come back and visit it in 10 more years.
Or, keep it, and study the ISSF til your eyes are dry.
You may get to hand that RoadMaster down to someone you love, even if only as a temporary beater.

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Marky Dissod

· #22 · 4 mo ago

In practice, any cheap & new injector set that is CLOSE to plug&play, consistently performs within 5% of OE injectors.
That means that the Long Term Fuel Trims would eventually settle and land between 121 & 134.
Tuning for such injectors is not strictly REQUIRED.
That said, even OE replacement injectors might be off by a bit ... hopefully, off by less than 5%.
For best results, however, tuning is always recommended.

Oh wait, forgot something:
One of the reasons why every LT1 (& LT4 & L99) will need new injectors, is E10.
OE LT1 injectors may wear out more quickly due to exposure to E10.
If the OE injectors can have their E10 susceptibility corrected (the gov't wants to make E15 mandatory soon), then they'll continue to be a decent replacement option.
Otherwise, my educated guess for desirable replacement injectors would be L9H / L94.
It goes without saying that best results always require tuning adjustment.

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Marky Dissod

· #23 · 4 mo ago

Two interesting things come to mind:

1. Using an adjustable fuel pressure regulator to raise reference pressure from 3bar / 43psi to 4bar / 58psi
Even prior to tuning, raising reference fuel pressure to 4bar / 58psi improves OE injector performance, by which I mean they spray better, which leads to drivability improvements.
Even before updating the injector constant to 28.6, this underappreciated mod might even pay for itself if the driver drives conservatively often enough.

2. Every injector is an individual, even after a good thorough cleaning, more info is needed for best results
In an ideal world, each injector with a given part number is perfectly identical and interchangeable with every other one.
In reality, they perform closely, but not identically to each other, and the PCM / ECM accounts for this.
To make a long story short, for V engines, installing any injector into any cylinder randomly is NOT optimal.
Again, even prior to tuning, each injector should come with its post-cleaning performance characterized.
PCMs and ECMs still think in terms of Left & Right banks.
With enough info about each injector's test performance, you can decide which injector goes into which cylinder.
At the very least, the injectors should be grouped 'Left' & 'Right', so the left & right banks perform as similarly as possible.
Installing the injectors thoughtfully improves drivability and performance, even before tuning.
(Injectors that perform within 2% of each other definitely require less tuning.)

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Marky Dissod

· #26 · 4 mo ago

storm9c1 said:
Logic dictates that all 24lbs injectors are the same.

Unless specifically referring to LT1 24lb / hr injectors, no, this statement is not automatically true.
Two 24lb / hr LT1 injectors may be 'close enough', but most likely NEVER identical.

storm9c1 said:
Just wasn't able to find the happy 128 even after weeks of driving.

Injector-to-injector variance is only one of a few reasons why 128 is so elusive.
Since LT1 operating systems were spec'd designed and written prior to E10, that's another reason.
122 - 134 should be easily achievable (although 122 is preferable to 134).

E10 (or E15) is not the end of the world.
Just saying that injectors that were not designed for E10 should be rebuilt with E10 in mind if possible.

storm9c1 said:
My advice / lesson is just to watch your BLMs.

No matter what, this is great advice.

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Marky Dissod

· #28 · 4 mo ago

For 325 peak horses or less, then OE injectors are all you need, and GM already tuned for them.
(Although GM's tune can still be refined, it calls for TunerPro $EEhack and experimentation.)
For those who want more than 325, some GM injectors idle better, and make more power, than LT4s.
Unfortunately they won't work that well without tuning.

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