Quetion, are the 3100 series injectors on mid 90's FWD GM motors adaptable to work on the 2.8L ? I got a 3100 series motor at the shop, and since I'm getting ready to port the upper/lower manifolds, I figured Id Swap injectors too (I've been running lean...). The motor in question was used in all kinds of GM cars, they are quite plentiful in my area. The Houston area Has the emissions Dyno Test too, would that kill me?

 

if you're running lean, you might wanna check your 02 sensor. or your injectors may be getting clogged up or something, just putting bigger injectors in probably will cause you problems.

 

I've been ALL through the car dude...The only thing left is lean injectors (by flow chart anyhow...). I was just wondering if anyones had any luck usingg them.

 

No, 3100 injectors will be to big, make it run overly rich.

Will they fit in the holes? YES

 

Could just put in an adjustable fuel reg and crank the pressure up / the NO2 kits for our cars come with a restrictor valve that reduced the return flow and raises the pressure when you hit the gas.

Or maybe you reg is failing???

Your pump has enough PSI but after the reg the injector side PSI is down???

We run at 130-145 line psi what is it at the injector / what is the stock reg set for???

 

Might wanna run a couple cans of seafoam [napa] through the tank to clean up anything in the fuel system.

 

the vacume line to the regulator could be cracked, or gotten knocked off.

I've had that happen twice in past month

 

Huh? I take it 3.1 injectors aren't the same size as 3100 injectors then?

 

tom, they are wanting to know if they will fit on a 2.8

It will go in the hole, it will spray, but it will spray to much.

Injectors in 3100 and 3.1 are same as I know.

 

.....Anyhow....Hey Tom, have YOU tried running 3100 series injectors? I imagine the computer would automatically compensate for the extra flow (Tom, correct me if I'm wrong??) I could care less about running a little rich, THATS the point. I WANT the car to run a little rich (if thats even possible...).
You see, the odd thing about my motor is that it is showing a 14.7:1 AF ratio, but I still get the code 44. It has nothing to do with sensor input, The only things left to cause it are mechanical. If I run it hard when it's lean, I'll burn a valve (REALLY don't want to rebuild the heads...). Anyways, anybody who HAS used 3.1 injectors, talk to me. Thanx

 

if you look at the last post tomp created, you will see that he is asking the same as you. So we can assume he hasnt.

I installed 3.4l injectors in my 3.1l engine. I am telling you the reaction I got from it.

The ecm will compensate a little, yes, but not what it fully needs.

You could very well just have dirty injectors, and they need professionally cleaned.

 

How much would that cost? I don't want the car out of commission for more than a half day. The motor i got is Clean as a Pin, the injectors are new, and I fig'd Id just swap the originals for the time factor.... If it runs rich, I don't mind, if I pay to have them cleaned (I assume I have to send them somewhere ) and it runs lean, I'm pissed. Thanks for the info Though.

 

I wouldn't be doing stuff like that cause of a code. The computer is not always right. Matter of fact the computer is pretty dumb if you ask me. Come drive my car and then pull the codes. it says me computer is bad/fried but it drives like a dream or a raped ape. depending on pedal position.

 

Yes, they would have to be sent out to be cleaned PROPERLY. Cost is like 11 an injector

Now, the difference between 3.1 and 3.4 injectors is 2lbs worth, made mine run rich.

The difference between 2.8 and 3.1 is only 1lb. It will prob still run slightly rich, but not as much as mine. If you can get some injectors for cheap, give them a try. I understand your frustration of coughing up a chunk of change, and it still not perform as you want it to. Getting some used 3.1 injectors is prob less expensive then cleaning what you have. May do the trick, may over-do the trick.

You could possible just install a holly adjustable regulator on your current ones. Or get used 3.1 injectors, plus regulator, and tune the pressure down.

 

He's right, FBodTrek, I haven't. And I -can't- run rich, they throw us on the dyno for emissions in NJ. So now that I know they run rich, I gotta dig up a lowmileage set of 2.8 injectors from Somewhere!! Either that or buy new at $60/pop...

I would've thought the injectors would've varied the pulse length and kept the car from running rich; but maybe that's out of spec for what the computer can compensate for? Eventually (laughs) when I rebuild my 2.8 (I've been saying <i>that</i> for years), I'd be doing some headwork, so the 3.1 injectors might help me then. But now, I can't see dropping that much for new 2.8 injectors. I should do a lookup at gmpartsdirect.com to see how much $$ they want for a set.

 

Well Tom, this is what I found out from my friendly neighborhood parts dealer: "Depending on the type of injectors YOU have in your motor (86?) They could be the SAME as the 3.1 injectors. Turns out the 86 powerplant came with TWO different types of injectors!" The 3.1 only got one type, SO- What you do is, Pull out an injector, call whatever parts dealer you use, read him the part number, and tell him to tell YOU what the part # was for the 3.1 series motors. (I used Hi-lo) If you have the same number as the 3100 series YAYYYYY! All you gotta do is check. (Also, I talked to my inspection guy, he doesn't think it running a tad on the rich side will kill us on our 2.8's, but i suppose I'll just do it and find out) Good Luck!

 

They ran two different part #'s? Wack

Give it a try and let me know your outcome.

Like I said, 2.8-3.1 is 1lb

I did 3.1-3.4, and thats 2lbs.

 

There are two diff injectors for the 86. Two different part numbers, one of them is the same as the 3.1. I went around and around with the manager of HiLo(good friend of mind) We broke out ALL kinds of parts catalogs, checked the computer many times. Believe me, I was more surprised to hear that than you can believe....Now, Ijust gotta get around to seeing which ones I have.

 

Yea, that is surprising.

Ask around and see if their is two different ECM prom codes for a 86 2.8. May be easy/simple as swap in 3.1 injectors, and change bin on ecm (change prom chip for you) and done.

You also said you dont mind if it runs tad rich, throw some 3.1's in it and give it a try. I would advise (but dont have to) reset the ecm if you stick 3.1's in it.

 

You should care about the care running rich because it'll fry your O2 sensor and the cat WAY before they are designed to die.

If you are showing 14.7:1 a/f ratio, then you are running dead on and NOT lean. You have nothing to worry about. If you are getting code 44, then you have a problem somewhere else, it's not in the fuel system if you are showing 14.7:1. This is assuming that you have used some sort of diagnostic tool like an exhaust sniffer of some sort.

 

Fantastic! Thanks for the info, FbodTrek!!

 

I have 3.1's in my 2.8. They came in the 85 2.8 that I swapped into my car. As far as I can tell, the car runs rich, but not rich enough to cause a problem when driving. However, I am fairly sure I will FAIL the Wisconsin smog test.
Tom, you could BORROW my old 2.8 injectors if you have Rich clean them and have them back to me by JUNE

 

Since 14.7:1 is "optimal" for fuel economy and emissions, I wonder what is "optimal" for power? I imagine it would vary from engine to engine, but it would be nice if there was some test data out there to show calibrated power curves over different Air fuel curves. Heck, run a really hot spark with a richer condition (it could happen...). Honestly I don't care about emissions or fuel economy (Otherwise I'd drive a 4 cyl...). For all we know, there's power to be had running rich (with the exception of blowers/turbos of course). Anyhow, just a thought....

 

When you go WOT, you want around 12:1 a/f ratio...

 

Thanks for the offer, Damien! I'll let you know if I've gotta take you up on that!

 

The price isn't to bad for this little beauty to be very useful.

http://www.tazzo.com/tazzo/efi.HTM

Tazzo Electronic Fuel injector Monitor

Measures Fuel Injector duty cycle in real time (0 to 100%).
Individual warning lights for 85% and 95% levels.
Measures the oxygen sensor voltage output.
High speed display.
Filter electronics to stabilize the signal at WOT.

 

Awesome find! I couldn't find any spec sheet on the site though (as in, how it connects)... did I miss a link, or are they just not telling us?

Did a search, found one review on a DSM website: http://www.dsmreviews.com/dsmreviews...azzoEFIMonitor Seems like we get four wires, but only one is for the injectors. So I guess we'd just be measuring one bank of injectors? Or does this get tied into one SINGLE injector? Hm...