Curious if anyone has run into issues with timing after changing injectors? I purchased a 89 C4 about 2 months ago and decided to replace the injectors since it wasn’t running great and not holding pressure. I discovered the old injectors were 24lbs and stock should be 22lbs, so I went back to 22lbs refurb injectors from Fuel Injector Connection. I am wondering if the tuning/timing is specific to the size of injectors, maybe? After several attempts and multiple new parts, I cannot get her to start.

Here’s what I have to-date.

Performance was sluggish and fuel pressure wouldn’t hold.
Replaced the old 24lbs injectors with refurb 22lbs.
Replaced EGR valve and fuel pressure regulator while the plenum was off.
After checking for leaks and pressure it started and ran but performance was worse.
Seemed like the firing order was off or something so replaced the spark plugs, cap, rotor and coil and triple checked the wires.
Also replaced Oil Pressure Switch because of oil eak.
Confirmed the rail is getting fuel and holding pressure.
Confirmed new spark plugs are getting spark.
It just cranks and still will not turn over.

Anyone else experience something like this?

 

Did you disconect the ESC before setting the timing and reconnect it after?

 

Injectors have specific delay time and spray patterns which related to their tuned injector lag and phase. If the new injectors don't match the anticipated injector delay period then tuning will be off. It would need re-tuning. However with such small injectors this is very rare and wouldn't likely cause a no start issue. You may have some wiring backwards or something if it wont even pop or fire with good fuel pressure. Or maybe the fuel injectors aren't injecting enough fuel.

Did you try pull a plug and see if it has fuel smell on it? Wet with fuel plugs? Did you get any backfire? did you try a clear flood? (clear flood is hold throttle to floor then crank to clear the fuel from the cylinder)

 

Check for gas in oil, and change it if suspect…that could kill compression. Double check no fuel in vacuum line to FP regulator (new one could be bad).

 

I 100% agree with this. I would add that even if two sets of injectors are the same flow rate they very well may require different tunes. I've seen this first hand when using a factory Delphi 36 lb injector and then using a Holley 36 lb injector. Both have flow numbers at the same fuel pressure. But the delay time was very different (along with other factors). This caused a rough idle and poor performance but it would start and run every time.

Even comparing two different injectors from the same company can have drastic differences. Again the Holley 36 lb standard high impedance vs the Holley 36 lb Sniper pico. Both high impedance at the same flow rate vs pressure. But both require very different data for the tune.

So it's very possible that you will need a tune with your new injectors. But by the sounds of it you have something else going on that's making it not start though.

 

I sure did not. That's where my mechanical abilities start to fade. I can replace parts but not experienced with tuning and timing. Is it possible to reset the ESC? I have already disconnected the battery and reconnected. Is a timing reset always required over replacing injectors?

 

It did run after I installed the new injectors but it was sluggish so I replaced the plugs, cap, rotor, coil and now it will not turn over. I did check the new plugs to see if they were fouled and put them back in. I have not tried the clear flood. So holding the throttle to the floor will clear the fuel and not add more?

 

Do you have a shop book for the car? Before you do anything else pick one up and read about how to set timing. This alone might fix your issue.

 

You should routinely check the distributor timing anyways. even if the engine runs. It must be precisely set. It is very important to know the timing of the engine, at all times. hehe times

Yes clear flood is a common well known algorithm for any ECU. After say 60 to 70% throttle the ECU will stop injecting fuel completely. This way the engine only pumps air. It will clear the fuel from cylinders if there is flooding.

 

There is no fuel in the FP regulator vacuum, but I do believe I am smelling fuel in the oil. Hope I am wrong. I just changed the oil and it is not cheap these days!

 

I do not have a shop book but came across some good videos specific to the C4. I agree, I am thinking it is timing related.

 

With an 89, the ecm must see more than 8 distributor reference pulses in order to provide any crank fuel.

Do you see any rpm activity on the tach while cranking?

;----------------------------------------------
; CRANK FUEL PW MULT Vs. REF PULSE LT 17
;
; 10-18-1997 Dissassemby of ARAP Lines= 16
;
; TBL = 256 * MULT
;---------------------------------------------
ORG $038B ; MULT DRP'S
;---------------------------------
LC38B FCB 0 ; 0.000 1
LC38C FCB 0 ; 0.000 2
LC38D FCB 0 ; 0.000 3
LC38E FCB 0 ; 0.000 4
LC38F FCB 0 ; 0.000 5
LC390 FCB 0 ; 0.000 6
LC391 FCB 0 ; 0.000 7
LC392 FCB 0 ; 0.000 8
LC393 FCB 128 ; 0.500 9
LC394 FCB 128 ; 0.500 10
LC395 FCB 64 ; 0.250 11
LC396 FCB 64 ; 0.250 12
LC397 FCB 64 ; 0.250 13
LC398 FCB 64 ; 0.250 14
LC399 FCB 64 ; 0.250 15
LC39A FCB 64 ; 0.250 16
;---------------------------------------------


;----------------------------------------------
; CRANK FUEL PW MULT Vs. REF PULSE GT 17
;
; TBL = 256 * MULT
;----------------------------------------------
ORG $039B ; MULT DRP'S
;---------------------------------
LC39B FCB 51 ; 0.199 1
LC39C FCB 51 ; 0.199 2
LC39D FCB 51 ; 0.199 3
LC39E FCB 51 ; 0.199 4
LC39F FCB 51 ; 0.199 5
LC3A0 FCB 51 ; 0.199 6
LC3A1 FCB 51 ; 0.199 7
LC3A2 FCB 51 ; 0.199 8
;----------------------------------------------

 

Thanks for the stats! I just checked and no RPM activity while cranking. Does that indicate the timing being off?

 

Thanks to all for the feeback and suggestions. I have a list of checks to run this weekend.

Here's what it sounds like by the way (hope it's not a problem to share this) ...

 

Sounds like the timing is too far advanced.

 

Agree with Tom. (timing)

 

I think I have it sorted out. I’m certain my wires were out of order. I used a screwdriver in cylinder 1 to find TDC then discovered that the rotor is pointing at the 2:00 position (standing at the front/driver side on right). My wire/cylinder 1 was not at that position. I changed the order to start 1 at 2:00 then 8-4-3-6-5-7-2 clockwise. Before I try to start is there anything I should unplug/reset?

 

Remember--TDC can also be exhaust stroke TDC--
Are you on exhaust or compression TDC?

Back to no RPM when cranking " I just checked and no RPM activity while cranking."
ECU needs to see RPM signal or will not fire injectors
Is there spark at the spark plugs?
Are primary wires/lead correctly seated into distributor cap?
Is there voltage going to distributor?--large red wire battery voltage at all times when key is on
Back to basics..........................
Sort ignition issues then onto fuel issues

 

All great points.

How do I know if it’s exhaust or compression TDC?
Does the RPM signal go through the Ignition Control Module? Mine looks pretty rough
If not the ICM, what other factors might affect the RPM signal?
Yes- the plugs do have spark
Yes- plug wires are seated on the distributor cap
I will check power to the distributor tomorrow (need to buy a new voltage meter)

Thanks a ton for the guidance!