QuestionI have a 1989 GMC 1500, 305, auto, nothing fancy. I have an intermittent starting problem. The truck was running rough at low idle speeds so I changed the EGR valve and that problem was solved. But, I now have an issue with having to crank the engine for 10 - 15 seconds before it starts. I had a helper look at the injectors while I was cranking over the engine and he said that for a good 10 seconds or more there was NO fuel coming out of the injectors, and then when the fuel finally did spray out the truck started of course. Here is a list of things that have been replaced... TPS, EGR Valve, Fuel Pump & Sending Unit, Temp Sensor, Oxygen Sensor, Spark Plugs, Wires, Rotor, Cap, MAP Sensor. I think that is all.
Thanx
Terence
AnswerHi
The PCM uses the ICM (ignition control module) for injector pulse.
It pulses every TDC #1 cyl fire.
THAT being said, it also needs 9-13 psi to pulse. If there is too much pressure it will not pulse as it overcomes the spring in the TBI unit (fuel pressure reg is spring operated).
So I would check fuel pressure first, making sure it is 9-13 psi.
If so check the fire also, see if it is firing for those few seconds. If not suspect the ICM which is located inside the distributor assy.
If so I would look at the pressure regulator bleeding out. The regulator in those units have a rubber diaphram which over time tends to weaken. The springs also break.
It is a fairly small investment,(PROBABALLY under $100.00) but I would purchase a TBI rebuild kit and fuel pressure regulator anyways and get the unit rebuilt or rebuild it yorself, if able to.
IF you do not have 9 OR IF it is over 13 WHILE CRANKING, suspect the fuel pump. If you can keep a pressure gauge on it see if it bleeds pressure down within a time period ( I Like to use 1 hour) If it bleeds to -0-, check the pressure reg OR the pump.
I Hope this helps.
Just advice from experience.
Good Luck
Pawl
