well you know the old saying dont go looking for trouble, or you will find it??? Well i have been reading some posts here about how not so great injectors we have in these C4s. And since i have only owned my '90 C4 for a few months, i am now getting into some serious concerns. The injectors actually look different to me, like i have 3 of one and 5 of another. They have a different body color to them, and the metal is different. I will try to attach a picture of the 2 different kinds.
So now where i found the trouble, was in the coil resistance. I had my good DMM home from work, so i decided to measure them all, with a cold engine. Got some varying numbers for sure:
Cyls 2,4,6,8 = 14.8, 16.4, 12.5, 12.6 ohms
Cyls 1,3,5,7 = 16.1, 16.4, 2.4, 16.0 ohms.

Now i assume the 12-16 ohmers might be correct, but i sure dont like that low one at 2.4ohms. i even double checked it.
Just what i wanted to find out........

 

Call John at FIC and order 280-155-715 and reset your flowrate to 24.4 lbs.

 

Call Jon and get a new matched set. If the injector is that low cold it will most likely be almost a direct short hot. This will pull down some of the other injectors. Jon's prices are great and the difference the new injectors make is incredible. Just replaced mine two weeks ago and it is like a different car. It really is like a new vehicle. I thought it ran good before, no problems, but what a change over the stock crap that GM used. Call Jon!

 

Those all look like mismatched accel injectors...not good.

Like they ALL say......

Call Jon !

These inj have many ways to cause problems...the fact that the inj itself can clog, stick and short internally is the common way. Because of the way the system is wired and designed, 1 bad inj can cause the set of 4 on that side to short out and FLOOD the eng with raw gas.

ANY C4, repeat, ANY C4 is now old enough regardless of miles to justify the $250 cost of calling Jon and getting late model alcohol compliant injectors that will likely last longer than the owner...(whats another 25-30 yrs?)

You'll see many running/starting issues clear up after you install and clean up the fuel system. A new pump may be necessary if yours is weak, and a filter anytime you go in the tank.

 

I think injectors that lasted about 20 years would not fall into the "stock crap" category. It would be great if everything on a car should last that long. But I do agree, call Jon and get some new ones.

 

Just because they ran for twenty years doesn't mean they ever ran right. GM must balance quality over cost and these were what they chose. I believe they could have used better parts. As stated earlier, I thought I had no problems with my original until I put something better in. Now the car is very responsive to throttle changes and as far as I can tell works better all around than it ever did. Quicker starting, smoother running, and better gas mileage. If I had known this before I would have changed them when the car was brand new, although maybe the originals were the best available at the time. Once again, even if you don't think you need them, I highly recommend replacing all of them. You will be glad you did.

 

I agree with all above regarding calling Jon. I bought a set from him earlier this year and they did wonders for my 92.

He is at the bottom of the links at the left. Fuel Injector onnection.

 

Well that is the right thing to do, for sure. but what is the consequence of running these injectors like this for the summer? I was planning on taking the top of the motor down this winter, for gaskets and some maint, and then send the injectors out for service. I forgot these were batch fired systems, so each side fires togethor. It could affect things more than i know.
Now the last owner did not touch the injectors as far as i know, so who knows how long they been like this. Car runs decent, but certainly not perfect. Working on the tune now in the PROM. It does have a rich smell at startup, but FP is good, and holds after shutdown. Gas milage could be better for sure.
So does this Jon person at FIC take my stock injectors on trade? Or give me some credit for the old ones?
I did my L98 camaro injectors a while back, sent them to Cruizin Perf. Was happy with their work. I want to drive this car, not keep working on it!

 

My concerns for your original post are as follows: You have at least 2 different types of injectors. The OEM Rochester's ohm different than the replacements, but one you show as 2.4? That should clearly set off a red flag, or maybe it was an error in typing?

History: GM started with Bosch, and in a cost cutting move in mid year 88 went to the Rochester. By the late 90's these had such a high failure rate GM finally switched back to Bosch. I have the newer type III's in my 04 LS1. However, in my somewhat L98 I have a type II Ford pink I run at 48 psi. I don't buy into the whole ethanol hype unless you are running E85. 10% has proven not to be a problem, and I think is more of a conspiracy theory kind of thing.

If in fact you have a bad one, and it wasn't an error I would replace them all now. Why waste time tuning if it is a known bad set? I recommend the Ford 24 lb blues, because I know for a fact the yellows run lean. While they're a huge improvement over a bad set. Most comments I see say somethings still not right. As a tuner you know how a vehicle reacts once we get the fuel maps as close to 128 BLM as we can.

On the other hand, you own time is free. However, tuning in the Summer is better, because it will only be slightly rich come colder weather.

Here's the set I like:
http://fuelinjectorconnection.com/sh...p?productid=57

 

Good info there, *****, and i do appreciate all posts. Are those Bosch design III the same as the p/n someone mentioned above? I looked at the video at FIC. The USED Bosch units out ran the re-cond others!
In my C4, i have 3 of the black bodies and 5 greys. Sure that raised a flag to me weeks ago. And no, not a typo on #5 grey, the coil R=2.4ohms. Tonight i checked it again, but hot, and was about 2.4-2.5 ohms. i checked another nearby and it was 16.5ohms. I am guessing the coil has some shorted turns in it. NOT good!

Also, you dont want to hear this, but i refuse to put FORD blue parts in my Chevy. Not how i was brought up. My ride sits in the winter, since i live in snowbelt, from like mid-Nov to april, so i got lots of time then to work on it. I just want to run it now. in early August i have a show i must be at! i can take it easy on car, not drive it much, and certainly not rev it out high.
My 88 IROC must have the early Bosch units in it, since they are still going good. But they have been sent out for service. It is a MAF car, but i been tuining it for long time. NOt perfect, but hard to get all BLMs=128 with MAF. It does run real smooth tho.
So can you get the fuel rail/injs up and out without pulling the TB? I just hate working with engine coolant.

Interesting thoughts on the E10 fuel. I dont like this alcohol one bit. Havent seen many problems with my autos, but some of my small engines were affected. I keep my IROC up good, so havent seen any probs yet.

 

You could run the Bosch yellows and tune your VE tables up. If you get to 99.9 just add to you power enrichment. I'd be curious to see a duty cycle percentage. Is this motor stock?

 

It is mostly stock. Just have Borla cat-back exhaust and K+N air filter. I just recently ported out the plenum when i had it out. I dont plan on doing much to this one.....but then again plans change. I have AFPR waiting to go on. And i am doing the chip thing as you know.
This winter the plan was to pull the base manifold, and replace all gaskets, and port eveything out/gasket match.
Are the blue design III really Ford injectors? Doesnt say so on FIC, but i like the price. He also showed brand new Delphi units 22#s, direct replacement for L98 TPI, E10 compliant, only cost $399!!!

 

First, E10 compliant is BS. The oil industry is doing everything possible to discredit ethanol. I've seen the scare tactics that it will blow up your lawnmower, to damaging anything built prior to E10. What they're afraid of is E85, so the E10 campaign is just nuts. Come on, we got Iowa rednecks against Wall Street oil tycoons. It also increases octane rating.
Off soapbox!
It's my understanding that the 280-155-715 is the replacement for the 280-150-947 which are both Ford racing 24 lb injectors.
What's worse, I didn't tell you that the 280-155-700 Bosch yellows are Ford 4.6 pullouts. Personally, I think these are all new overstock being bought from Bestliquidators.com for pennies on the dollar for resale to the unknowing.
Almost forgot, the Delphi's remind me of Rochesters. Why would we pay more for an inferior product?

 

There are quite a few people on this site that are using the Bosch III reman's that Jon fabricates and all seem very happy with the results. These are what I just installed and they are a great deal for less than $200.00.

 

When you've datalogged your vehicle and proved that your blm averages are within a reasonable amount of 128 then you can prove my testing different. If you think Jon loving takes apart each Bosch yellow 280-155-700 and somehow makes it better than the known 204 cc injector that it is let me know.

I had someone send me these, and I spent my time freely to datalog these with a perfectly tuned 90 AXCR Corvette file. I logged very high BLM counts in the 150's and some cells hitting the max add wall of 160. While the ECM may make up for a majority of this undersized injector it is not what the ecm was designed to do. While it may be well improved over a poor running injector, it is not a direct replacement.

Come on, you've put a 280 ci injector into a 350 ci motor.

 

Long lasting is not an assurance of good. I don't care if it lasts 100 years but the spray pattern is bad or the fuel volume is inconsistent.

 

MrWillys
I don't know anything about the Bosch yellow 280-155-700 injectors. The ones I'm talking about are the Blue Bosch III's. Jon takes them apart and replaces the seals with new material's. He then flow test them and chooses matched sets and sells them at a very good price. If you have any problems with Jon's injector's he is one of the easiest vendors to deal with. As far as I know he backs his products without any hassle and makes himself available for any questions or help you need. If you received a set of undersized injectors simply contact Jon. Unless of course you ordered that specific Bosch number. Also I put a 24pound injector in a 24pound motor as suggested by Jon in an e-mail, not a 280 ci injector into a 350 ci motor. Are you sure we are talking about the same product. I have seen no other person but you talk about Yellow Bosch Injectors. Did Jon spec these for your vehicle?

 

My mistake, you must have an LT1 running the 280-155-715. I have Jon linked in my website and think he's a great guy. However, the 700 isn't a direct replacement for 85 thru 91.

Anyway, enjoy your Friday!
Scott

 

So you are saying that the blue reman design III Bosch units are better than the 2 new injector choices that Jon at FIC sells? I have been surfing his website alot lately. I think common sense is finally setting in with me. I am going to call him soon and get the right injectors. Like you said, why spend all this time tuning the PROM, when i know i have bad injectors. Why wait till the winter. It is not that bad of a job to change them. I will get new O-rings and a filter as well.
Now if all my stock multecs were the same, and had good coil reisistance, then i would not likely change them now. Just tune the chip and service them over the winter.
I am trusting all you guys on the C4 forums that i am doing the right thing.

 

I don't know about MrWilly's but I and quite a few other members of this site think the Blue reman Bosch III's are an excellent deal. I can not speak of the quality of the new offerings because I have had no personal use or read of anyone on this site that used them. I do know that the Blue reman Bosch III's work quite well in my 96' LT-1 and I see no reason to spend more money on other injectors. If I had a modified motor I might think differently but for a stock engine the Blue reman Bosch III's are perfect. The link posted earlier by MrWillys are what I am talking about. Buy them, install them, and be happy you did.