I've been trying to sort out a problem that was causing a smog test failure for Carbon Monoxide. It turned out that my #1 injector was completely plugged and the computer was injecting extra fuel because it was reading the fresh air coming down the pipe.

So, I need to replace a set of injectors. I've got a friend who can hook me up, I just need to make a selection. It's my understanding that the early design L-98 injectors are a design that is prone to fouling, and that a later redisgn also had better atomization. Can a later set of stockers be retrofitted into my '87? What do I ask for?

 

I would go with a set of 24's or 22's. Racetronixs and summit both carry these.

 

What size are the stock injectors? I've heard that larger injectors will throw off the mileage readout on the dash. They'd be kind of a waste anyway, since the motor is totally stock, with the first generation aluminum heads and the stock intake and roller cam. That setup won't flow enough to justify larger injectors.

I'm hoping that somebody could tell me if the 2nd generation injectors would work with my stock intake and computer. My understanding is that the stock GM 2nd design injectors have a more efficient spray pattern. Does anybody out there know if this is true?

 

Stock injectors for your year were 22 lb/hr
I don't know what you mean by "second design". The preferred injectors are of the Bosch design. The multec's that GM went to in the late 80's were crap. They then went back to the Bosch.

 

Put your injectors in a box and send them to Rich at Cruzin Performance. He does great work and the price is reasonable. He will clean them and put them on his flow bench. Alot cheaper than replacing the whole set. I sent the injectors from my '87 and he did a really good job. Haven't had any problems since.

 

If you are going to replace them try the ford motorsport blue top injectors (24lb) with an adjustable fuel pressure regulator

 

Using slightly larger injectors like Ford Motorsport 24# injectors in place of your 22# injectors is a very cost effective option. Once it goes into closed loop mode, the ECM will use the O2 sensor feedback to adjust your injector pulse width to correct for the larger injector size. The mile per gallon readout will be off slightly, but it will have no effect on your odometer. If everything else is working correctly, only at idle and WOT will you be running a little too rich. The ECM will compensate for even that issue by adjusting the BLM (Block Learn Multiplier) and Long Term Fuel Trim values which it uses to determine non-standard fuel operating conditions from the last time the car was operated. Since FMS injectors are rated using a fuel line pressure of 39psi and the 87 stock pressure is 43psi, some guys use the 19# FMS to achieve a more near stock fuel mix before the ECM even starts to make adjustments.

While an adjustable fuel pressure regulator is handy, your stock ECM can pretty easily handle the differences caused by using 24# or 19# injectors without one. GM had to build fallback reliability into the original system to compensate for aging fuel system components and unserviced air/fuel filters.

I agree with Morley, the second generation Multec injectors used in 89s and later C4s were much less reliable than the earlier Bosh units. What your source may have been talking about is the fact that the early C4s were batch fire and the later C4s were sequential fire. This is an aspect of how the ECM/PCM activatess the injectors and the later sequential method is superior.

I would follow SS409 425HP's advice and "Put your injectors in a box and send them to Rich at Cruzin Performance. He does great work and the price is very reasonable compared to buying new." Rich is very well known and has a quick turn around time. I had him rebuild my injectors and the ones on my sister's Caravan.

 

At the time, the second design was I believe the "Lucas" injectors.

 

artvette, Yes you are correct. My post was misleading in that respect. Some early C4 Bosch injectors had problems and were replaced under Factory warranty with Lucas designed injectors. In 89 GM went to Multec injectors and used them for several years after. Most of the info I have received says that the Multec injectors were a poor substitute and Rich and some other injector rebuilders all agreed that the Multec quality was so poor that it was better to replace them and not attempt to rebuild. The 87 & 88 Bosch injectors can be rebuilt.

 

Thanks for all the input. I ended up trusting my buddy who runs a parts house, and he set me up with a set of injectors that lack the plastic tips of the orignial (I suppose Bosch) injectors.

The set I'm removing are slightly taller overall, but both O-rings, the retaining clips, and the electrical connections are all the same size and style, and they are located in the same relative postions.

The set that I'm installing have a blue plastic ring around the body of the injector below the electrical connection. The top of the injector ends in a wide flat flange just above the top O-ring. And finally, when looking at the bottom end of the injector, there is a squared white plastic piece set in the bore, and the tip of the needle is concealed inside that piece. The tip of the needle can be seen in the plastic end cap of the old injectors.

Can anybody help me identify these new injectors?

Also, I broke the retaining clip while trying to install the first replacement injector. Probably a "dealer only" item, right? Anybody know of a readily available substitute? I'm hoping to get this back together in the morning. Not many Chevy parts counters open on Sunday around here.

 

Go to your local hardware or Home Depot and pick up a piece of flat thin Al sheet stock, mark the outline of an injector retainer clip and cut it out with a sharp utility knife.

The clip only holds the injector roughly in place so it's shape doesn't have to be exactly as the OEM. When I first pulled the injectors from my IROC I broke several of the clips before I got the hang of it and my home-made substitutes worked well.

 

Hell, i threw all of my injector clips away, don't need em.

 

A couple of questions about this: Anyone have a part number for the blue tops? Also, what are the best options for the AFPR on an '89?

 

For an L98 the Holley is the best looking AND in my opinion best performing AFPR.