lq4 engine fuel system problem
Thread Starter
Teching In
Joined: Mar 2013
Posts: 3
Likes: 0
lq4 engine fuel system problem Hi i have a problem with a lq4 engine from a 03 silverado
cillinder 4 gets soaked with fuel first i tought i had a bad fuel injector
so replaced all 8 but i have still the same problem,
also replaced plugs , wires
when removed all plugs and turning over the engine, cill 4 get soaked with fuel
where should i look next ? checked compression on all cillinders and there good and have no dtc codes
thank you in advance Sander,
cillinder 4 gets soaked with fuel first i tought i had a bad fuel injector
so replaced all 8 but i have still the same problem,
also replaced plugs , wires
when removed all plugs and turning over the engine, cill 4 get soaked with fuel
where should i look next ? checked compression on all cillinders and there good and have no dtc codes
thank you in advance Sander,
TECH Addict
Joined: Mar 2013
Posts: 2,628
Likes: 30
You have a grounded circuit. The injectors are fired by the pcm grounding them. You have +12 at the injectors all the time the key is on. Either the ground wire for cylinder number 4 is grounded someplace OR the pcm has failed grounding the circuit all the time.
Sounds right ^^^^^^^^^
If you have a test light, connect the clip end to positive, and test the leads for the injector to see if it is permanently grounded. If it is, then trace the wiring back to the firewall/ecu and make sure there is no pinched wiring for that injector against the block or anything metal.
If you have a test light, connect the clip end to positive, and test the leads for the injector to see if it is permanently grounded. If it is, then trace the wiring back to the firewall/ecu and make sure there is no pinched wiring for that injector against the block or anything metal.
Thread Starter
Teching In
Joined: Mar 2013
Posts: 3
Likes: 0
thanks for the input
i have checked the voltage at all injectors with the ignition on (engine not running) i measure 6.6 volt at all the injectors
and when i run the engine it fluctuates between 6.6 and 12 volt
i have also checked all wires from the injectors back to the connectors of the pcm
and they are good.
it seems the pcm opens the injectors way too long at cill 4
and a little less on 6
could it be that the pcm is way off ?? if thats possible
when i run the engine for a couple of minutes and the pull the plugs
it pukes fuel out of cill 4 and less on 6
the story is i have bought the truck to use the chassis and driveline
for a project, putting on a 47 ford coe cab on it
and eventualy need to send out the pcm to get it run stand-alone
i have shipped the truck over from the usa to the netherlands
and it runs like this since i have it and dont know its service history
so if it could be that its caused by the pcm ? i might better shipp it out
to get it re-programmed and check from there ?
i have checked the voltage at all injectors with the ignition on (engine not running) i measure 6.6 volt at all the injectors
and when i run the engine it fluctuates between 6.6 and 12 volt
i have also checked all wires from the injectors back to the connectors of the pcm
and they are good.
it seems the pcm opens the injectors way too long at cill 4
and a little less on 6
could it be that the pcm is way off ?? if thats possible
when i run the engine for a couple of minutes and the pull the plugs
it pukes fuel out of cill 4 and less on 6
the story is i have bought the truck to use the chassis and driveline
for a project, putting on a 47 ford coe cab on it
and eventualy need to send out the pcm to get it run stand-alone
i have shipped the truck over from the usa to the netherlands
and it runs like this since i have it and dont know its service history
so if it could be that its caused by the pcm ? i might better shipp it out
to get it re-programmed and check from there ?
Teching In
Joined: Sep 2011
Posts: 2
Likes: 0
Have you tried swapping the injectors with a different cylinder? Could be a jammed open injector, or trash in it.. Try swapping them from 4 and 6 over to different cylinders where the problem is not occurring. dont forget to lubricate the O-ring upon installation so as not to damage it and cause a leak.
