Hi,

I need the forum'sexpertise (read through a lot of threads concerning the TPI running too rich but it would be great to get some tips to steer me in the right direction

Car ran good normally with just a few minor issues: hard starting, slight stumbling on idle from time to time, slight vibration and it would die on really infrequent occasions after a long drive on idle but only like twice a season).
Tried to get my yearly inspection and failed the emissions because of running too rich on idle (as soon as you gave a little bit of throttle it burned it off and the values were "ok").
The mechanic gave me the hint that maybe one or more of my injectors were leaking so I ordered a bunch of new bosch ones (first from southbay but unfortunately they got lost and then from ebay, 19 lbs like thy should be for my 305)

Installed them and noticed the following:
-Old Gaskets were completely shot (replaced them completely)
-The injectors which were in there were the "fatter" type, so 22lbs? (like for a 5.7)

Started it up and it ran like crap, idle was extremely bouncing around (between 600 rpm and 1200), resetted it (with the correct procedure) and it is better but far from good. My main issue is that it runs extremely rich.
Data logged it with WinAldl and I got a "Rich Flag", interestingly though the BLM stays at 128, what does this mean, shouldn't the ECM try to correct it??

What I've tried so far:

• Checked for leaks with Engine cleaner, looks like everything is nice and tight as it should be
• Checked for vacuum lines missing, looks like I connected it back together correctly
• Checked a plug, looks ok not sooty or something, doesn't smell like gasoline
• Disconnected the MAF, ran worse, so I would assume it's not the issue

What should I do next? (my biggest issue is that I have to wait extremely long for parts since I'm in Austria/Europe )

• I already have a quite new adjustable fuel pressure regulator in there, will check the pressure next week (originally the car ran way too lean so we cranked the pressure up a little, maybe thats too much now with the new injectors)
  • +As stated in other thread, deconnect vacuum line, prime, if fuel comes out the regulator diaphragma is dead
• Take out one of the runners again and check the spray of the injectors?
  • First check resistance and listen with stetoscope if the open/close + see if they loose pressure too fast
• I have a vacuum tester, is there some info which lines to test and how the result should look like?
• Shouldn't be the case since I marked everything but is there a way to crosscheck which injector cable belongs to which injector easily?

Any other ideas?

 

Those Bosh 3s' are notorious for causing issues just like you are having. You will need a tune to correct your issue. Usually they run lean but the other problems you have to me are a direct result of the voltage offset difference between the stock Multecs. The stock injectors are wide body and that fact does not mean they are a higher flow just a different design. The spray pattern is different on the Bosh 3s'. Your Fuel pressure should be turned back down to 43 or so @ WOT as the injectors are designed to run @ that pressure. Turning up the pressure will affect the way it runs and maybe not for the better.
There are a couple of tuners on this board and I worked with Tuned Performance, Brian was great. Record your data run and you can e-mail it to him. Since you are overseas, if you order the chips and a chip burner, he may have these for sale, Tuned Performance can e-mail you the file to burn your chip. This way if it takes few tunes you can work through the e-mail so there is no shipping back and forth. He sends you a file, you send it to the burner, burn the chip, install into the cars computer and Wella!
If you do a search for Bosch 3 injectors on here you will see a host of threads with others that have had similar issues and they are all solved with a tune. FYI the Delfhi's are direct replacements but also cost over 2 times as much.

 

@vinny R Thanks, thats great advice, didn't know that they are not quite plug and play

Concerning the Delfhi Injectors, were would I get those? (at least on Ebay I only find Accel and Bosch)
Tuned performance, will keep that in mind as a last resort

 

I got mine from Southbay Injectors. TGO members get a 10% discount. They are the #19 versions.

 

Are they in fact Bosch III? Maybe post what you actually bought.

 

the issue is the offset info, all 19 pound injectors are not the same. if you had a good running car you would have been better off paying to have your original equipment parts cleaned, flowed, and balanced. that would be the easiest way to keep it right.

I mean think about it, there is a 30 year gap in the technology of your original injectors and what is sold now days.

 

These are the ones I got:
https://www.ebay.com/itm/8pcs-Upgrad...72.m2749.l2649


It for sure had some issues + there isn't a shop I can think of here which does this kind of work (at least not for private enterprise). There isn't a comparable car culture here (and especially not for foreign cars, mostly european models like BMW's and VW's etc). I would love to have access to some american scrapyard

What I really don't get is why the BLM stays at 128, shouldn't it be trying to adjust??

 

Irrelevant, we are not talking about converting to direct port injection here. Engineering and physics have not changed in 30 years and the injectors still work exactly the same.

The ECM must have the correct flow rating constants adjusted based off size and pressure, and then the ECM needs to how long it takes to fire the injectors at a given voltage. If this information is off, it will not function correctly, same as 30 years ago. Then we can also talk about how different injectors behave for PE and AE... but this was all relevant 30 years ago too if you went from one injector style to another.


I would be having a look at your O2 Voltage because, yes it should be. Once the 02 sensors is warm and providing feedback. The 02 sensors on these cars are good for about 2 years/50K miles and are sensitive to being killed by silicon. If you don't know the health of the O2 sensor, it might be part of the issues you are having.

 

Yeah those are bosch III. My friend bought those same ones and when I put in my voltage offsets for my injectors it cleared the problems right up. This would require retuning on your car.

As was said earlier, the reason you're not getting into closed loop (which is most likely why your BLM is stuck at 128) is either because the computer is not seeing the correct coolant temperature via bad sensor or wiring, or because the O2 sensor or its wiring to the ECM is bad. ECM depends on both those sensors to get into closed loop.

 

So, just tested a few things out:

• Checked the Resistance of all Injectors, all are around 16 Ohms, only one slightly less at 14,5
• Checked with a stetoscope if all of them are running (which they are)
• Connected my new fuel gauge since the old one doesn't show anything, was off by a huge margin (like 55 psi)
  • Now its ~34 with vacuum on idle and ~45 with the vacuum disconnected, spot on correct?

After this adjustment the car ran actually fine, no bouncy idle, way less smell of unburnt gasoline and doesn't shake that bad anymore. (so quite a better result )
Unfortunately when I tried to do a small test drive it wouldn't run on all cylinders after a few meters and was smoking quite badly, fiddled around with the plug wires, which helped for a bit but not too long (the headers were already too hot to get my hand in there properly).

One thing which just confuses me is that the pressure drops to zero (from priming the pump) in like a split second, but if it was leaking that badly it wouldn't have been able to run correct? Also there was more than enough fuel in the test line when I disconnected it so maybe the gauge is not holding the pressure?

@ULTM8Z What does the offset do actually?
@KyleF Good to know, I have a new one lying around anyway, will make sure to replace it!

 

The voltage offsets are basically a way of communicating to the ECM the firing characteristics of the injectors for different operating voltages. Each injector P/N has a characteristic operation that varies over the various voltages it can see on a car. It's a function of it's nozzle design, internal electrical solenoid, etc...

The same injector will deliver different amounts of fuel for a given on-time commanded by the ECM, depending on the operating voltage coming out of the alternator. When the ECM commands the injectors on, it simply exposes the injectors to the full available system voltage (whether it's 12.8V, 13.5V, 14.2V, etc... whatever is being produced by the alternator and seen by the ECM). So the ECM needs to know the injector characteristics at these various voltages, that way when it commands them on to deliver a certain amount of fuel, it actually knows how long to command them on for to get that correct amount of fuel. Simply the ECM knowing the flow rate is not enough information. Particularly when a car's system voltage can vary significantly with underhood temperature, prevailing electrical load (i.e., when fans are on, headlights, stereo, etc)... or even if there's an electrrical malfunction and the alternator fails and now you're running off the battery and down to 11V or less (car still needs to be able to "limp home").

And different injectors will behave differently from one another over these voltage ranges. So this table in the calibration "Injector pulse width correction vs Battery Voltage" allows you to define your injectors to the ECM.

Below is my table with the values for my injectors. The particular to the p/n of the injectors I bought. My friend and I couldn't find the datasheet for his injectors, so we put these values in and that got is car back to normal (it was a bone-stock factory 305 TPI). So they must have been close enough.

The other thing we typically do is to zero out the "Low pulse width injector offset vs BPW". 2nd table below. The Bosch-III's are so much more efficient than the factory Multecs that they don't need any "help" at low pulse widths. That table will allow you to add on-time to whatever the ECM calculates it needs for a given condition. For example, for a given condition, if the ECM calculates it needs to open the injectors for 1.71 milliseconds, you can put a 1/2 millisecond in that table for 1.71 milliseconds and the ECM will then tack on an extra 1/2 milliseconds. As I understand it, In the $8D code, GM was programming in additional on time for pulse widths less than 2.2 milliseconds because at those low pulsewidths, the injectors weren't quite delivering the expected amount of fuel, so the engineers just manually added additional on-time for those low pulse widths to compensate... it was kind of a band-aid for inadequate injector technology.

 

@ULTM8Z Thanks a lot for the explanation, more than an interesting read!

I will take yours and Vinny R's advice and try to get a chip burned for me if the stock tune is not working out!

 

I highly recommend a custom tune regardless. The car runs that much better. However, when I swapped in my Bosch 3's the car ran fine, it was just lean. You do need to make sure the injectors are all seated correctly or you could get a vacuum leak. Just rotate them by hand a little and ensure they all feel the same. That is a quick and easy check. Also, make sure you have a factory OEM Bosch MAF. The aftermarket ones are just crap and although the custom tune will help fix it, the OEM Bosch MAF's are much better across the board.

To answer your question, in TPI you cannot mix up the injector wires (that is why they are not labeled). All four injectors on one side fire as all four. It's only if somehow you can reach across the engine and plug into the other bank. 1-3-5-7 all inject at the same time. Same for 2-4-6-8.

 

Thanks for the Info!
After I can actually test it running on all cylinders, a custom tune will be really high on my To-Do List
Concerning the seat of the injectors, that's what I was fearing but the rings are clipped in like they should be (still I can turn them all around quite easily, more so than the old ones I think)
The MAF is a Bosch one from the stamping on it, don't know how old it is though, but since it worked before the change I will at least assume that it still is "ok"

The more you know, was not aware of that, especially since the video I used as a guide (which quite nicely explains everything) made a point to mark them

 

Might take a look at this. Just my opinion, but it works:
https://www.thirdgen.org/forums/diy-...injectors.html

But bottom line, if old-school injectors are replaced, related calibration values have to be changed to provide a new "tune".

 

Very interesting thread you linked, thanks!
Brian from tuned performance was so kind and provided me with a shopping list which I will order as soon as I can confirm that my ALDL cable is working with tunerpro (always used winaldl) and when the engine is running on all cylinders again.
I'm quite worried that the immediate loss of pressure and this issue may be related (that they would leak so bad as to flood everything, hopefully only my pressure gauge is at fault...)

 

You can rely on Brian and Southbay. Stay away from the Ebay junk as you now know.

 

Conclusion to yesterdays tinkering, the Ebay Bosch Fuel Injectors are bad, at least one of them is leaking the complete pressure (and fuel) into intake...

That means new injectors (most likely from southbay)
(will also change the EGR when I'm on it and properly clean everything in the meantime)

 

Don't buy anything that doesn't include voltage offset data.

GD

 

^^^^^
What he said!

 

So, a little update:
Wasn't hard to find the injector which was leaking it was still wet after the last start of the engine last week...
A little bit of luck though as the package from southbay arrived right on time (after everyone thought it was lost by the postal service)

And I really have to say, these Bosch injectors are a b**** to get seated properly, needed like three tries as there were leaks from the rail....
Got everything back together today, started it up and it was smoking like crazy (fearing one of the new injectors was leaking again), but it stopped after engine was warming up as it probably burned off the sea of gasoline the ebay injectors left behind...
Now it's running fine, taking throttle, starting right up etc

One thing which is really giving me a headache:
Before the final install today we tested the pressure again to see if it would hold and yesterday evening it was "ok", it took like 10 minutes to drop 10 psi and went a lot slower after it hit ~20.
When I tried the same thing today (doesn't matter if the engine was running or if only the pump built up pressure), the pressure drops to zero like way too fast (~10 seconds), as it is not smoking like crazy anymore, running fine and starting right up after losing the pressure, it would seem like the culprit is the return line?
(if an injector would be leaking again it would run like crap again, correct?)

I read that this can be tested by blocking the return line and just letting the pump build pressure, I ordered some clamps for that (hopefully the line does not leak afterwards, it feels quite solid) + if that is actually the problem, how can I fix it?
(The only difference from yesterday was that my tank is nearly empty now)

 

IMHO I don't think it is an issue. As long as it holds the proper pressure while running does it really matter how long you have FP in the lines after you shut it off? Why would you want 40+ lbs of pressure when your car is just resting. Seems more of a hazard than anything. The key on pump prime system takes care of getting the pressure up before you start.

Did you have to remove your gas cap when you changed your injectors? If your fuel system is properly sealed you should have had to. If not the pressure from the tank will force fuel to flow through the line.

Mine drops like a pebble I shut the car off and yes within 10 minutes or so the pressure is gone. I think the reason I have FP leak down is I have a small vapor leak in my filler neck so the entire fuel system loses pressure when I shut the car off. I don't get the pressure release when I remove the gas cap after about an hr or so of the car being shut off
I am saying this because you said the only difference in your test was an empty tank, the fuel system will need more time to build and hold that pressure when there is more air in the system.

 

Yes! have to use plenty of lube and really need 4 hands.

Yes, if leaking it should not run OK. But what you are describing generally points to one of the following: 1)fuel pump check valve failure 2)fuel pressure regulator leak 3)injector sticking open at key off. For 2), disconnect vacuum line. Should be no fuel.

See attached.

 

It doesn't matter if the fuel pressure drops after shutdown. Modern turbine style replacement pumps don't have check valves and they work just fine. My 400 HP daily driver with FIRST manifold, fuel rails, and external regulator bleeds the pressure off immediately on shut down (high volume turbine pump with no check valve). What matters is the pressure when running. What the pressure does after shut down is of ZERO concern.

GD