fuel injectors
 

I returned from another great time at Funfest '07 with some new parts
and ideas for my 89 coupe. Went to Gordon's seminar and he always
talks about checking fuel injectors. So on the way home stopped at
Sears in Terre Haute and bought an Ohm meter and when I got
home checked my fuel injectors. 5 read 16.9 which is great but three read
8 to 12. So now with this knowledge, how easy is it to replace the
fuel injectors? I'm not much of a mechanic but I did buy this car to be
my new hobby. Gordon also recommended Lucas injectors but I can't
find any listing for these, he did say the kit from Mid-America which uses
Accel's were fine.
I'm getting 20-25miles/gallon and car ran great on road trip around Illlinois
but I guess I'm running on borrowed time if 3 injectors are going bad.

RE: fuel injectors
 

Hi Fun...It's really not that hard, but It's not something you're going to do in a couple of hours. The plenum has to come off, maybe even the runners. You'll need new gaskets for the runners.

I need to replace my injectors too, but when I do I'm going to replace the EGR valve and temp sensor under the plenum, maybe even the fuel pressure regulator, while I have everything off

RE: fuel injectors
 

Pulling injectors ain't tough. BUT, tie some string or fishing line to a paper clip, and hook it to each injector retainer clip, BEFORE pullingthe clip. If the clip goes ballistic, you could lose it.

I don't know if I'd worry too much about a few extra ohms at the injectors. I think vacuum leaks are more a problem with TPI's than anything else - I'm sure GK probably mentioned this, didn't he?

Did you happen to record his stuff?

RE: fuel injectors
 

Mating surfaces must be IMMACULATE at re-assembly. Like where the injectors O-ring seats in the intake. A speck of grit will allow a vacuum leak, and that's a tune-killer. As are gasket surfaces...

RE: fuel injectors
 

No I didnt record Gordon's talk but I sat in on 2 this year and 1 last year,
I've thought about signing up for his week-end class. Has anyone been to
his class?

How do you check for vacuum leaks?

RE: fuel injectors
 

It's a bear to find leaks. One method is with a propane hand-held. Attach a 2 foot length to the nozzle, crank up the idle till it's steady idle, then feed the propane into areas where components meet - throttle body to intake, intake runners, etc. An idle speed increase means a leak. They're VERY HARD to find.

If you do have a leak, there's NO reason to do ANY mods at all till they're tight.

You got a lopin' idle? If not, you're probably OK.

RE: fuel injectors
 

One easier method is use a piece of 3/8 fuel line about 3' long. Put one side to your ear and the other to listen around engine for a hissing. The hose isolates the area just where you are listening. Another way is to use carb spray, but be very sparing with it. If you find a leak, the spray will change the idle, smooth it out.

RE: fuel injectors
 

propane, like in a gas grill or hand torch?, Does the propane get sucked
in and rev the engine?

RE: fuel injectors
 

Exactly. And youcould use a grill propane tank just as readily as a hand-held torch. Ya' just gotta' get some rubber line long enough so you can put the tank on the ground. You won't be able to hold it up long enough to do a complete check. Just barely open too.

Does your idle hold steady?

RE: fuel injectors
 

yes, my idle is pretty steady, if I sit at a light for a long while it sometimes
drops from 8 to 7 but it doesnt lope.

RE: fuel injectors
 

Mech was right about the listen for hiss test. I forgot about that one.

And if your idle holds steady, you're in good shape. What do you think mech, about his injectors' ohms variations???

RE: fuel injectors
 

Anybody got any recomendations pro or con on fuel line additive injector cleaners?

Didn't really know if they are good preventative maintainance only or possibly a quick fix to
a potential problem with dirty injectors?

Opinions please....

RE: fuel injectors
 

Hi rudedog, the injector cleaners you buy at the parts store are only good for maintenance, if that. If you want them cleaned good take it to a professional and get it done right, they have the good stuff.

On another note, I read somewhere, and I can't remember where, that some of those injector cleaners you buy at the parts store can foul the spark plugs.

RE: fuel injectors
 

According to Gordon Killebrew, he said not to use injector cleaners,the
only thing to keep injectors in shape is the drive your car and keep
gas running thru them, and storing your car is hard on the injectors,but
in the north where you cant drive year round then start your car and pull
the fuse that runs the fuel pump and let the car think it is out of gas, this
will dry the injector and help it last longer.

RE: fuel injectors
 

Hi all I to have heard not to use fuel injector cleaner I have read it is hard on the 02 sensors. sense we are talking about fuel injectors mineohm OKbut I am getting hyd lock in the cylinders and alsofuel Gage bleeds back onfuel press ck.I know every thing has pos and neg just your thoughts on pintale injectors verses disk injectors . I think I will replace mine and cant decide which way to go. I'm not looking for big hp the LT1 runs fine the way it is.What are your thoughts on injectors???
Thanks
Ric W

RE: fuel injectors
 

Hyd lock? If you're talkin' about what I think you are, you know you can pop a pushrod with that problem? Especially with high compression...

Do you have a leakin' injector?

RE: fuel injectors
 

HiCWB
I think I do have a leaking injector or more then one.I don't drive the vette much but the last time i drove it and it was hot from city driving . it didn't want to start after it was shut off for about twenty minutes. It acted like it was flooded and then started. Doing a fuel press check after the pump stopped (just with key to on position) about 2 seconds the press bled off. That is why i suspect hyd lock or leaking injectors.I have 80,000 mileswithoriginal injectors and thought I might as well change them all. Iwas thinking about disk style injectores. What do you think? Do you think sending them out to get them cleaned would help leaking injectores? I do think I'm leaning towards new ones.
thanks
Ric W

RE: fuel injectors
 

I thought hydraulic lock was when the combustion chamber filled with fuel, and locked the engine up. Water from a cracked head will do the same thing.


Mine did it once, I had to remove the spark plug toblow the fuel out

RE: fuel injectors
 

The fuelpump check valve, and the fuel pressure regulator, will also cause the pressure to bleed off quick too.

RE: fuel injectors
 

Hi Ric, here's some good info on the different types of injectors.


There are three basic valve designs used with variations on each: pintle, disk, and ball.

The pintle-type valve is the earliest design but still popular. The problems with the pintle design include increased chance of clogging in the small orifice area, slower response time because of heavier armatures used to lift the pintle, and reduced service life.

The ball-type injector uses a ball (actually half a sphere) to seal the metering orifice, rather than a pintle. This allows the use of a lighter armature and so response time is faster than for pintle types. There is also less wear for a longer service life. The orifice can be designed with multiple openings for a wider spray pattern plus more fuel can be delivered for a given drive time.

The disk-type injector eliminates the armature and the solenoid acts directly on the flat disk through the core of the injector body. The flat disk rests on a seat that has an orifice in it. This arrangement is even lighter than the ball-type for an even faster response time. This disk and seat design also results in less deposit build up at the orifice and longer service life.

RE: fuel injectors
 

Thats what i am talking about ( fuel building up in the cylinder) thats what I called hyd lock. Is there a way to check for injector leakage other then sending them out? rshiver thanks for the info it helps me allot on my decision on what to purchase. I think I have decided on the disk type to replace with and not bother with sending them out I have dealt with Racetronix in the past and that is what they sell and I have thought very highly of them. (I'm not plugging anybody ) I raced mg and formula fords for many years before I retired. I wish I could have run aC4 on a large closed circuit race track like Mid-Ohio or Road America. I have never driven aC5 or C6 but i know the C4 is very well balanced.

Ric W

RE: fuel injectors
 

Ric, I don't know any other way of checking the injectors, and as far as I know, thats the only way fuel can get into the cylinder and cause hydro lock.

RE: fuel injectors
 

Yeah - that's what I was thinkin' he meant. I shoulda' said alsoconnecting rod, not pushrod.

2 seconds, and all the fuel pressure is bled off???I've changed a fuel filter after it was settin' all night, and it STILL has pressure. Do you actually get 0 pressure in two seconds after shut-off?

If you think a cylinder is gonna' fill with fuel and cause a 'lock' condition, I think you should NOT turn the key. You can lose a connecting rod, or worse...

RE: fuel injectors
 

There is a procedure for checking fuel pressure leakdown. The way to check injectors is to attach a fuel pressure gauge to the rail. You'll need 2 needle nose vise grips. Block off the return line (smaller line), turn the key on and block off supply line. If your pressure drops, then you have a leaking injector. If you don't have a leaking injector then your leakdown is from either the pressure regulator or the check ball in the fuel pump are bad. You can isolate by using one of the vise grips. Just on return line and pressure drops, check ball is bad. Just on supply line, then regulator is bad. These are assuming your injectors check out.

RE: fuel injectors
 

Thanks mech very helpful i will take a look into thisas soon as i can. I probably will have to use plugs on the lines thereare no fuel linehoses in the Eng bay. I do have press and return hoses at the tank do you think the test would work pinching the hoses way back there?
Thanks Ric W

RE: fuel injectors
 

Does fuel rail pressure drop to 0 when you turn off the key?

If it does, how can you get so much fuel leaked from injectors to cause a lock-up condition in a cylinder? And how come you're supposed to let off fuel pressure before doing a fuel filter change or other fuel line work? All them chilton's and hayne's [joke] books say that the fuel will spray when you breach the line.

If a regulator stops fuel pressure from going above 50 psi, for example, then when you kill the motor and the fuel pump stops pumpin', what happens then to let off the pressure that's still there, which is UNDER 50 psi???


EDIT: I'm thinkin' here - (see the smoke:D) -
Is the regulator mechanically controlled? Or is it electrical, and it opens up and lets the pressure off when you kill the motor?

That still doesn't explain why you're supposed to bleed off pressure.................................

RE: fuel injectors
 

Hi CWB
The fuel press drops to about 15 lbs after you turn of the key very quickly and that is not normal. I would like to isolate the reg and injectors like mech suggested but there are no rubber hose lines in the Eng bay.GM calls for a tool for this purpose that goes on thQD on the fuel line. It ismade by Kent Moore but the tool is to much $$ just to check one time. Over $200. There are rubber hoses at the tank just under the fuel door and cap. I might be able to pinch them there I will have to check this out. CWB the press reg looks like it is vacuum and it probably returns the fuel to the return line after no Eng vacuum. If the diagram was leaking I would probably have fuel in the vacuum line and I don't. I still think fuel injectors but i am going to try to figure a way to isolate them as mech 859suggested. I have a question on the check valve. Is it actually in the pump and is the ball valve at the top of the tank a rollover valve ?

RE: fuel injectors
 

Ric, you can do what mech said where the rubber lines go into the tank, and the way I understood Mech is, the checkvalve is on the pump itself.

RE: fuel injectors
 

Thanks rshiver I just replaced the fuel pump last week because it only was getting to 35 lbs. if check valve is in the pump that should be covered. I did see a ball valve at the top of the unit and thought it was the roll overvalve.
Am I allowed to make a suggestion to the threadson ware to purchase items if I'm not connected to the company in anyway?
Thanks Ric W

RE: fuel injectors
 

Hey Ric, if you just replaced the pump you can pretty much rule it out as your problem.

I don't think mentioning where you bought a part, or that you got a good deal on so & so, at so & so every now and then,is against the rules, if it is then I'm guilty. I would think as long as you're not trying to promote your own business, or advertising a website or business in your signature, there shouldn't be any problem.


This is what I found in the Forum rules.

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RE: fuel injectors
 

35 lbs is the normal operating pressure for L98's. If it is @ 35, unplug vacuum hose to the pressure regulator and see if pressure rises 3 - 4 lbs. If so, the pump is probably ok.

RE: fuel injectors
 

The pressure is controlled by an engineered compression spring and engine vacuum. The vacuum overcomes the tension of the spring via a diaphragm, hence the regulator leakage. You can test that by just pulling vacuum line from regulator to see if fuel is present.

RE: fuel injectors
 

Gotcha[sm=interesting.gif].

Not'cher first day, huh?