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914World.com _ 914World Garage _ #3 cylinder injector quirk
Posted by: moneysmarts Jul 20 2007, 10:11 AM
I thought I had a bad injector on #3. With the motor is running, when I pull the lead to #1, #2, or #4, the engine stumbles as you would expect. If I remove the connector to cylinder 3, however, nothing happens. Even though I was getting a decent spray pattern when I pulled the injector out, I decided to replace the injector. Still nothing. There IS spark at the plug. And my noid light shows that there's electrical pulses at the connector lead. 
On the back of the block, under the air cleaner, I have three pairs of white wires that are solidly grounded.
Any ideas fellas?
Thanks
Posted by: dr914@autoatlanta.com Jul 20 2007, 10:25 AM
I thought I had a bad injector on #3. With the motor is running, when I pull the lead to #1, #2, or #4, the engine stumbles as you would expect. If I remove the connector to cylinder 3, however, nothing happens. Even though I was getting a decent spray pattern when I pulled the injector out, I decided to replace the injector. Still nothing. There IS spark at the plug. And my noid light shows that there's electrical pulses at the connector lead.
On the back of the block, under the air cleaner, I have three pairs of white wires that are solidly grounded.Any ideas fellas?
Thanks
Switch the inj leads front to rear and see if anything changes. If so a lead problem, if not check the compression and check more importantly for intake leaks. Also make sure that you have not installed two bad injectors in a row. Some rebuilds spray fine but when installed do not work properly. Also make sure that the spark for all four cylinders is the same and that the spark plug gap is not closed!
Posted by: swl Jul 20 2007, 10:27 AM
I guess "#3 isn't firing" wouldn't be a welcome quip.
So you have spark, you have fuel being delivered. You should be good to go. Is the spark plug wet?
Posted by: moneysmarts Jul 20 2007, 10:31 AM
George:
Thanks for the quick response.
If I switch the leads from front to back, that is move the gray covered lead from #4 to #3, the same situation occurs. pulling #3 cyl. has no effect on idle, and pulling #4 causes stumble.
In other words, even if I reverse the leads on the passengers side, I still have the same issue. 
Oh, and plug gaps look ok.
I checked to see if there's spark by connecting my timing light to the #3 wire. It makes my light flash, so I think I'm getting spark.
I thought I had a bad injector on #3. With the motor is running, when I pull the lead to #1, #2, or #4, the engine stumbles as you would expect. If I remove the connector to cylinder 3, however, nothing happens. Even though I was getting a decent spray pattern when I pulled the injector out, I decided to replace the injector. Still nothing. There IS spark at the plug. And my noid light shows that there's electrical pulses at the connector lead.
On the back of the block, under the air cleaner, I have three pairs of white wires that are solidly grounded.Any ideas fellas?
Thanks
Switch the inj leads front to rear and see if anything changes. If so a lead problem, if not check the compression and check more importantly for intake leaks. Also make sure that you have not installed two bad injectors in a row. Some rebuilds spray fine but when installed do not work properly. Also make sure that the spark for all four cylinders is the same and that the spark plug gap is not closed!
Posted by: Vacca Rabite Jul 20 2007, 11:03 AM
to make bang, you need spark, fuel, and compression all at the right time.
Does #3 hold compression?
Zach
Posted by: Dr Evil Jul 20 2007, 11:06 AM
Valves on 3? Had you messed with the harness before this (rule out that the wires are all on the wrong sides) or was it running fine and then started to do this? Definitely check to see what color your spark plug is and if it is wet as suggested above.
Posted by: moneysmarts Jul 20 2007, 11:09 AM
I don't know for sure, Zach.
I suppose I can find a gauge and test it.
Posted by: moneysmarts Jul 20 2007, 11:14 AM
Was running fine.
Started to get intermittant bucking, like the tps was going.
Checked that out to be fine.
Did the valves this spring, and thought they were dead on.
I could recheck them.
I'll pull the plug at lunch and check the color.
Thanks
Valves on 3? Had you messed with the harness before this (rule out that the wires are all on the wrong sides) or was it running fine and then started to do this? Definitely check to see what color your spark plug is and if it is wet as suggested above.
Posted by: Dr Evil Jul 20 2007, 11:31 AM
Coolio, the plug will tell...
Not switched wires if it just happened so that rules out some ideas.
Posted by: moneysmarts Jul 20 2007, 11:55 AM
OK.
Plugs out. On the tan side, and dry as a bone...like no fuel.
Checked the spray again... this time nothing.
Tried another spare injector, still no gas.
I'll swap in a known working injector (from one of the other cylinders) tonight.
I can't believe I've got two bad injectors, though.
Could the harness have a break in it.
The noid light says there is power, though.
Coolio, the plug will tell...
Not switched wires if it just happened so that rules out some ideas.
Posted by: swl Jul 20 2007, 12:26 PM
It is actually easy to break a wire inside the insulator - Not that I would ever have done something like that 
Easy to check and maybe worthwhile to do just to make sure. Pull off the main connector to the ECU and measure the resistance to ground on pins 3,4,5 and 6. connected to the injectors they should all have the same low resitance - 3 ohms is what I measured on mine. Precise resistance is not important just that they are about the same. If #3 is much higher than the rest then you may have an answer.
given that you have had that connector on and off a few times ...
Posted by: dr914@autoatlanta.com Jul 20 2007, 01:13 PM
with a good spark then it has to be a bad injector or an intake leak. How about switching the injectors?
George:
Thanks for the quick response.
If I switch the leads from front to back, that is move the gray covered lead from #4 to #3, the same situation occurs. pulling #3 cyl. has no effect on idle, and pulling #4 causes stumble.
In other words, even if I reverse the leads on the passengers side, I still have the same issue.
Oh, and plug gaps look ok.
I checked to see if there's spark by connecting my timing light to the #3 wire. It makes my light flash, so I think I'm getting spark.
I thought I had a bad injector on #3. With the motor is running, when I pull the lead to #1, #2, or #4, the engine stumbles as you would expect. If I remove the connector to cylinder 3, however, nothing happens. Even though I was getting a decent spray pattern when I pulled the injector out, I decided to replace the injector. Still nothing. There IS spark at the plug. And my noid light shows that there's electrical pulses at the connector lead.
On the back of the block, under the air cleaner, I have three pairs of white wires that are solidly grounded.Any ideas fellas?
Thanks
Switch the inj leads front to rear and see if anything changes. If so a lead problem, if not check the compression and check more importantly for intake leaks. Also make sure that you have not installed two bad injectors in a row. Some rebuilds spray fine but when installed do not work properly. Also make sure that the spark for all four cylinders is the same and that the spark plug gap is not closed!
Posted by: 2-OH! Jul 20 2007, 02:36 PM
Bad connection on the injector wires at the plug...Pull the pins out and make sure you have good connections from the white wire into the pins...
Chased the same exact problem on #1...Turned out to be an almost completely broken wire going into the plug at the injector...
2-OH!
Posted by: moneysmarts Jul 21 2007, 11:46 AM
Two bad injectors.
One of them was totally dead.
One spit gas, off and on.
Installed a good one, everythings running fine.
Thanks for the input, all/
Posted by: Vacca Rabite Jul 21 2007, 01:14 PM
Rock'n! Glad you got it back on smooth.
Zach
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