Injectors not "firing"
05-28-2006, 08:11 PM
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Injectors not "firing"
Hi guys I'm new to the site, I've been lurking for a couple months while putting a 1972 Camaro 350 w/ early-90s TBI injection into an S10. I've got it 95% together and am having a problem with my injectors. When I crank the motor, the passenger side injector only drips fuel while the drivers side barely seeps any around the bottom. Not enough fuel to fire. Before I go any further here's my info...
Truck - 1986 S10 - originally 2.8L TBI
Engine - 1972 Camaro 350 Block & Heads
Intake - 1992 Caprice stock TBI intake w/ EGR
Distributor - 1990 GMC truck - small cap electronic
TBI & all TBI sensors- 1992 Caprice
Wiring - 1986 S10 w/ appropriate changes & new pigtails
ECM - 1227737 - late 80's 4.3L
Fuel Pump - stock 1986 S10
All new plugs, wires, cap, rotor and coil.
... Here is my diagnostic testing so far...
- The fuel pump is running and supplying a strong supply of fuel to the TB in both "priming" and "cranking".
- I have spark and the motor is in time at about 8* BTDC.
- The ECM outer shell is properly grounded (which I've learned the hard way to make sure of!)
- Using a multimeter, I tested the voltage at the injector pigtails. From what I read there is one wire on each (red and white) that is supposed to be 12v constant with the ignition on, and they do have a solid 12v. The other two wires come from the ECM and I don't know what the voltage is *supposed* to be, but they do have voltage that fluctuates while cranking from around 4v to 8v.
- I removed the injectors and cleaned the little screens on them. In the bottom of the injector "bowls/housings" on the TB there was a puddle of gasoline in each, probably a 1/4" deep.
- I've been reading about faulty pickup coils causing injector problems. I'll change it out this week just in case. I'd replaced everything else in the ignition and for $12 why not!
- There is no anti-theft or alarm equipment on the truck.
What are your opinions? I've spent alot of time on wiring and re-checking the wiring versus the schematics. I don't think it's a wiring problem, but the fluctuating voltage on the injector pigtails do raise red flags in my limited knowledge.
Truck - 1986 S10 - originally 2.8L TBI
Engine - 1972 Camaro 350 Block & Heads
Intake - 1992 Caprice stock TBI intake w/ EGR
Distributor - 1990 GMC truck - small cap electronic
TBI & all TBI sensors- 1992 Caprice
Wiring - 1986 S10 w/ appropriate changes & new pigtails
ECM - 1227737 - late 80's 4.3L
Fuel Pump - stock 1986 S10
All new plugs, wires, cap, rotor and coil.
... Here is my diagnostic testing so far...
- The fuel pump is running and supplying a strong supply of fuel to the TB in both "priming" and "cranking".
- I have spark and the motor is in time at about 8* BTDC.
- The ECM outer shell is properly grounded (which I've learned the hard way to make sure of!)
- Using a multimeter, I tested the voltage at the injector pigtails. From what I read there is one wire on each (red and white) that is supposed to be 12v constant with the ignition on, and they do have a solid 12v. The other two wires come from the ECM and I don't know what the voltage is *supposed* to be, but they do have voltage that fluctuates while cranking from around 4v to 8v.
- I removed the injectors and cleaned the little screens on them. In the bottom of the injector "bowls/housings" on the TB there was a puddle of gasoline in each, probably a 1/4" deep.
- I've been reading about faulty pickup coils causing injector problems. I'll change it out this week just in case. I'd replaced everything else in the ignition and for $12 why not!
- There is no anti-theft or alarm equipment on the truck.
What are your opinions? I've spent alot of time on wiring and re-checking the wiring versus the schematics. I don't think it's a wiring problem, but the fluctuating voltage on the injector pigtails do raise red flags in my limited knowledge.
05-29-2006, 10:25 PM
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Car: 1997 Camaro z28
Engine: 350 LT1 built to LT4
Transmission: a
Axle/Gears: 3.23 posi
I'm just wondering real quick, where is the ecm chip coming from? if it's from the 6, it might cause problems similar to what you're talking about.
the reason being that the 4.3 came w/ I believe the 55lb injectors and the caprice came with the 61lb injectors. the regulator is actually on the tbi but the fuel maps are still in the chip.
i've heard of this problem w/ people who've changed injectors on their 305's and from people who've switched to 350 tbi and kept the 305 chip(it came with the 55lb injectors too).
anyway, just an idea.
if you've got access to the caprice ecm, i'd use that one altogether...they're the same ecm(different chips), but why mix parts when you don't have to?
the reason being that the 4.3 came w/ I believe the 55lb injectors and the caprice came with the 61lb injectors. the regulator is actually on the tbi but the fuel maps are still in the chip.
i've heard of this problem w/ people who've changed injectors on their 305's and from people who've switched to 350 tbi and kept the 305 chip(it came with the 55lb injectors too).
anyway, just an idea.
if you've got access to the caprice ecm, i'd use that one altogether...they're the same ecm(different chips), but why mix parts when you don't have to?
05-30-2006, 07:54 AM
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Engine: sbc 350
the wires to the fuel injectors...
in operation, the 'hot' wire will be 'battery voltage',
the 'ground' wire will be alternating between...
open, ...reads 'batt-voltage' at the terminal.
and
grounded, about one volt above ground.
if you know what you are doing, you
can test fire the injector by grounding
the 'gound' terminal.
not recommended, unless you know what
you are doing.. more info if
anyone is interested.
in operation, the 'hot' wire will be 'battery voltage',
the 'ground' wire will be alternating between...
open, ...reads 'batt-voltage' at the terminal.
and
grounded, about one volt above ground.
if you know what you are doing, you
can test fire the injector by grounding
the 'gound' terminal.
not recommended, unless you know what
you are doing.. more info if
anyone is interested.
05-31-2006, 10:10 PM
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That is my first plan of attack - test the injectors, since they've been sitting for awhile anyways and are questionable. Either way I can rule that out. The ECM could be the problem. I do have a Moates Ostrich and a tweaked bin file for this one. My initial plan was to get this one running with the stock chip then tweak it with the Ostrich and software. Maybe I need to reprogram 1st.
I did get a new distributor w/ pickup coil. The other questionable piece of the puzzle is the new sensors on the TB. The TPS seems adjustable based on the slot openings for the screws. I've read that if it is sitting at over 80% that the injectors will not fire. Then again I am getting a signal from the computer so that may be ok.
I did get a new distributor w/ pickup coil. The other questionable piece of the puzzle is the new sensors on the TB. The TPS seems adjustable based on the slot openings for the screws. I've read that if it is sitting at over 80% that the injectors will not fire. Then again I am getting a signal from the computer so that may be ok.
to me! 
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