How do I check Injectors for leaks

[90Q45]

New to the forum... looks like you guys do a great job.

I have a 1990 Q45 that is getting too much fuel.. How do I check the injectors for leaks. Can I disconnect the fuel rail and turn ignition on to check for leaks?

Thanks,Bob

[Q451990]

That should work, but it'll take a lot of work to get there... what are the symptoms you're having? Is the Check engine light on? Does the car rev up to a certain RPM and then stop there (limp mode)?

Sometimes a bad MAF (Mass air flow sensor) will cause a rough idle and black smoke. In this case the car is running rich, but not due to an injector problem, just a bad input from the MAF. Try moving the connector at idle and see if the RPM changes. If so try cleaning the connector, etc.

Here's a pic of the MAF if you're not familiar with it... Ignore the stuff about the CAS and setting the timing, but you might check it's electrical connection too.

Heath

[Q45tech]

Install a fuel pressure gauge in feed line [t after filter] turn engine off, the 34 psi should remain steady for 15 minutes .....no injector leaks.

A more severe test would be to clamp off return line the pressure can go up to 60 psi turn off car and see if pressure stablizes and doesn't leak down.

Q don't usually leak, the gasket might leak but the pintles are pretty good about not leaking.

Lots of difference between leaking into runner and externally leaking around rail seal.

[90Q45]

I installed the pressure gauge as you instructed between the filter and the fuel rail. It rose to somewhere above 34 and then proceeded to drop off at a rate of approx. 1 psi per second immediately down to zero. There does not appear to be any external leaking. I guess the next step is to take off the intake plenum and fuel rail?

[DAEDALUS]

Dennis, in the test performed, what keeps the rail pressurized...I mean, what prevents the fuel from passing into the return line? I assume it's the pressure regulator. It has the ability to completely seal off all fuel flow back to the tank?

[Q45tech]

Thats how it works a plunger in a tapered socket spring loaded to 34 psi with 18 " HG vacuum...........as the vacuum declines in acceleration [throttle position] the pressure goes up progressively to 43.4 psi.

Actually a BG fuel pressure tank [used in rail and intake cleaning]can be adjusted in roughly 1 psi increments to check things.

You alternatively crimp the fuel lines with protected hose pliers to make sure the regulator and the fuel pump antidrain valve are working as they should........then you start test injectors.

You can crimp off the left to right rail feed rubber hose to check which bank is leaking...........then you listen to the remaining 4 with a stethoscope/metal probe.

[90Q45]

Q45Tech,

I hate to bother you again.... is there a trick to getting the plenum assembly off?

Thanks,Bob

[DAEDALUS]

The only trick is to have done it before at least once or twice, or to have someone there who's done it. Most people are scarred for life, and can often be seen wandering around their garages during the ordeal, dazed and confused, mutering phrases such as "rubber hoses" and "harness clip". Seriously, do a search on it; you'll be able to find some tips scattered about. I think Landtodd posted a good thread recently. It is a bigger undertaking than it initially looks. If you're going for it (and if you've started, then yes you are), you'll want to consider ordering a bunch of parts now from Scottsdale to replace while you're in there rather than do the job again in 6 months when your hoses crack. Again, do a search for the parts needed. Scottsdale does have an under-plenum hose kit, though it may not have all that you'll need. You'll also need to order new rubber plenum seals. Take good notes and digital pictures.

[90Q45]

You guys are great.... I did stand in the garage and mumble some things but took what you said to heart and decided to live life and also becuase I am out of work and I need to save the money. Well I took a leap and got the plenum off without cutting hoses. Yaa. Now I am thinking of placing a pan underneath the fuel rail with the injectors installed and turn on pump to see what leaks. Is this a good test or will I have fuel everywhere?

No longer a virgin.

[DAEDALUS]

I can't remember for sure, but I thought each injector had a rubber seal surrounding it within the intake runners. I assumed the rubber seals were fuel gaskets in some way. If not, it's a good idea. Give it a try, just be careful with the fumes. Unbolt the rail and rotate the front end upward while keeping the fuel lines in back intact.

[Q451990]

The only place that fuel should exit the rail is through the pintile tip on the injectors. As long as you don't take the injectors out of the rail, the system should still be sealed. There are upper and lower o-rings on each injector - a leak at a lower one should cause fuel to drip or spray into the runner when it's not supposed to. If the upper o-ring fails then fuel should come out around the top of the rail where the injector fits into the rail and the cap that covers it screws on.

The runners have a harder plastic gasket or ring that fits around the pintile opening... but that's not holding any fuel in other than just sealing the runner. At least that's how I remember the system.

So to answer your question 90Q45, you should be able to do what you describe and look for leaks.

Heath

[90Q45]

Thanks Guys,

I connected some long hoses to the fuel rail and placed it in a pan down on the garage floor. Turned the ignition to the on position to run the fuel pump and found one injector leaking through the pintel and another questionable because of the plastic around the pintel was cracked. So I ordered two from Scottsdale and they saved me approx. $100.

Thanks again.:ylsuper

[Q451990]

Good deal! Word of advice, use some di-electric grease or vasoline on the o-rings before putting the new injectors in. It's not unusual to pinch the o-rings and then you'll have fuel leaking around the injector. I guess the good thing is you've found a way to "bench test" them before you put them back on!

I've also found that at least on my injector failures, the plug on that cylinder needs to be cleaned or my dead miss was still there...

Heath

[90Q45]

Thanks guys, your advice has been very helpful. I found one injector with a pinched o-ring. The mechanic said the temperature sensor and one injector needed to be replaced for $700.00. With your help and a lot of work I saved a lot of money and the care runs great. All of your tips have really helped and I even have a few of my own if someone else is going to perform the same maintenance. I feel I owe you guys, so if there is anything you need from Texas please let me know.

[90Q45]

Woops, I spoke too soon. Now the car stalls intermittently while driving down the road. After which it will start and run for some time. The fuel pump is making some noise. How do I go about diagnosing this problem?

[Q45tech]

Part of the wholr process it teeing in a fuel pressure gauge and taping to windshield so you can make sure the pump has enough flow to maintain 43.4 psi at WOT and 6,000 rpm PLUS as measured between filter and rail input.

The fact that you can skike 65 psi rail returned pinched clossed [at idle] is an Inticator but not proof .

Remember idle flow is x , cruise is 3-4 times x, and WOT is 50-55 TIMES more required gasoline flow than idle. I believe this is not clear to most

[landtodd]

Wow. You got the plenum off without cutting any hoses? On your first time? My hat is off to you, 90Q45.

My experience was that plenum R&R is a job that suckers you in. The first 45 minutes go like gangbusters. Then when you're in too far to stop, that's when the crying starts.

[90Q45]

Just got lucky I guess.... Your right about the 45 minutes, but what kept me going was the support from this forum. Also I had another member call me for some hints and I offered to help him. He is going to try it without a manual. Guys will do strange things when they get a request for large sums of money from greedy dealerships.

Thanks Guys.Keep up the good work.