Major Engine Miss above 3K

[Bob Eyres]

After sitting for a few months my 91',(60Kmi.), Has got a serious miss in the secondary induction system.
Power key off- It runs normally. Power key on- Engine goes flat above 3K.,gug,gug,gug.
There are no warning lights lit.
I have a Coplon duct insert, so that's not the problem.
Yes, they are the original injectors.

It doesn't take a genius to deduce that the secondaries aren't working, but I'm wondering what the most common causes are for this condition.

It looks like there's a plenum pull in my future. Any way to avoid that?

TIA, Bob.

[VetteMed]

Didn't we discuss your injectors being the likely culprit in another thread?

[GOLDCYLON]

Replace your injectors as previously discussed. GC

[Bob Eyres]

Yeah, but I hadn't yet figured out that it was only in the secondary, and that the primary was fine.
Just thought there might be something that could be done before pulling the plenum.
BTW, the vacuum is fine, it pumps up and shuts off in 2-3 seconds.

any thoughts?

[XfireZ51]

Originally Posted by Bob Eyres

It doesn't take a genius to deduce that the secondaries aren't working, but I'm wondering what the most common causes are for this condition.

It looks like there's a plenum pull in my future. Any way to avoid that?

TIA, Bob.

NO unless the secondary pump isn't working. Have you checked that?

[PhillipsLT5]

If those are 91 original injectors, there toast

[Paul Workman]

Quick current draw check to verify normal pump operation:

1) Leave the ingnition switch in the OFF position and set the VOM to the 10A setting with the RED lead PULLED OUT of the VOM (protects the meter)



2) Connect the RED lead PROBE end to the POS terminal of the battery and connect the RED lead METER end to the "A" connection on the VOM

3) Connect the black lead of the meter to the RED pump TEST POINT near the diagnostic plug on the wire harness (near the ECM).



You should hear the pumps come on as soon as the connection is made to the pump TEST POINT (RED wire with the black connector - a yellow alligator clip connects the test point on the harness to the black lead of the VOM in the picture). Each pump draws between 4-5 amperes. In the photo we see both pumps are running as the current draw (both are Airtec pumps in this example) is well in excess of 8A; commiserate with current draw of two pumps.



However, if the current draw is ZERO, then neither pump is running - not your situation, but if the current is only 4-5A, then one of the pumps is not running. Logically, since it is the secondaries that are having the problem, then the secondary pump fuse (under the passenger hush pannel) is suspect and you'll need refer to the FSM to check it.

Once both pumps are running, fuel pressure should be about 52 psi, but verification is best done with the FP gauge taped to the windshield and checked over a few quick WOT pulls. This will verify the pumps are working under load, and the fuel filter (on the passenger side frame rail, roughly in line with the door hing line) is not impeding FP/flow.

Another thing to verify is are the secondary throttle plates actually opening on demand?

One thing at a time, I recon...

P.

[Bob Eyres]

Thanks Paul. I'm not familiar with that tester, is it commonly available?
From the responses, It looks like those original injectors may be living on borrowed time.
Understanding that this is a stock motor car with bolt ons, If I just go for a full replacement, I've got some questions on new injectors:

-What are the basic types available? Or are they all the same?

-What is likely to be the most durable type? I've had this car for 18 years, and I will probably have it for at least 18 more.

-What is the best type currently available?

-What is the cheapest, most reliable source?

-Are most new injectors flow tested and matched? If not, who offers that service?

Any info, or opinions, would be greatly appreciated.

[ZZZZZR1]

Bob

Call John @ FIC.

www.fuelinjectorconnection.com

(770) 888-1662

They sell stainless steel injectors and yes they are flow tested

Good luck

David

[Paul Workman]

Originally Posted by Bob Eyres

Thanks Paul. I'm not familiar with that tester, is it commonly available?

Yes, the Fluke 115 is in current production and is a bit of a Cadillac, far as VOMs go. However, Most VOMs you can pick up at an auto parts store or Radio Shack, for that matter will also be able to read 10A. You just have to be very careful to follow the directions when doing this test, and NEVER change modes with the leads connected to voltage as the meter can be damaged or at least a fuse be blown.

From the responses, It looks like those original injectors may be living on borrowed time.

Most definately!!

Understanding that this is a stock motor car with bolt ons, If I just go for a full replacement, I've got some questions on new injectors:

-What are the basic types available? Or are they all the same?

-What is likely to be the most durable type? I've had this car for 18 years, and I will probably have it for at least 18 more.

-What is the best type currently available?

-What is the cheapest, most reliable source?

-Are most new injectors flow tested and matched? If not, who offers that service?

Any info, or opinions, would be greatly appreciated.

Summing injectors up this way...

There are several options, but as Dave said, Jon at FIC can provide you with what you need; a "kit" if you will that includes the proper gaskets, O rings, etc. His injectors (he says) are refirbished, and come at a very competative price. Jon's reputation for customer care after the sale is stellar, should there be a problem, according to those that have used his injectors.

As for most reliable, I choose new Accel injectors, on Marc Haibeck's recommendation, and have been totally satisfied with their performance. The part number is #150821 from Summit Racing. Note: these injectors are not listed by Summit (or they weren't) for the LT5 application. And, as such, there is a plastic alignment rib on the injector that has to be ground off in order for the secondary connector to work (takes a total of about 5 minutes tops to do all 8). You'll need to order two sets of 8, coming to about $587 plus shipping for two sets of 8.

You'll need gaskets. Jerry's Gaskets can fix you up with the gaskets etc you need. Just let him know you're replacing the injectors, and he'll fix ya up (with the same "kit" he provides to FIC).

P.