99 Sunfire GT 2.4L, hard starting

Asked by Oct 05, 2011 at 08:54 AM about the 1999 Pontiac Sunfire 2 Dr GT Convertible

Question type: Maintenance & Repair

My car just started being hard to start. I hear the fuel pump pressure up, I have fuel
to the fuel rail. Just replaced the crank position sensor, had code PO335. I cleaned
the TB and intake. I have no MASS air flow sensor. Check vac hose to the MAP
sensor, idle changes when I unhook it. Most of the time I will turn the key on, wait
for fuel pump to shut off and it will start, I will have to do this 2- 6 times before the
car starts. Some times the fuel pump will not run. Some times it won't even start
when the fuel pump runs and builds up to pressure. Any ideas??  Thanks  Dave

2 Answers


Check the ignition control module,(ICM). I had a very similar problem with a 96 2.4 Sunfire. The engine became increasingly harder to start until it no longer started at all. It had symptoms of no fuel, and showed codes for the CKP , CMP, and VSS sensors. If a scan tool shows that the CKP count is active but there is no pulse at the injectors...most likely its the ICM that has failed. The ICM is located under the cam cover, and as far as I know,there really isn't anyway of testing its operation.There are only tests that eliminate the related componets such as CKP and CMP sensors. I strongly suggest that an OEM part is used as a replacement. If your in a pinch,there are used ones for cheap on fleaBay, but a used OEM part is better than a cheap aftermarket part from china, IMO.

1 people found this helpful.

I had a problem with a 2005 Sunfire not starting, I could turn the key off and on several time and eventually the car would start, the odd thing about it would start anytime on starting fluid. After hours of searching on the internet I replace the Crank sensor, Coolant sensor, Fuel pressure Regulator, Fuel filter, tried a new ignition Modular, bought a new fuel pump but never installed it, I have 55psi fuel pressure that fades down to 0 psi overnight. I gave up on it and took it to the local mechanic and he was just as confuse as I was. He thought it was the ignition SWITH but the security light was not coming on as it is supposed to when the switch goes bad. I gave him the OK to replace it as they are known to go bad in GM cars. He replaced the switch and it starts first time every time now. $128 parts and labor... Thanks Lawson Automotive (Lawson, MO). My conculison, the Cranks sensor tells the computer to send injector pulse, however when starting the car the engine is not spinning fast enough for the crank sensor to send the proper signal, so the computer gets it information to pulse the injectors from the oil pressure sensor. Once the engine reaches 300 RPM the crank sensor takes control. The starter spins the engine at 150 RPM, the starting fluid gives it the added boost to get it over 300 RPM. What happen to the good old days where all you needed was Spark and Fuel... Points and Carborlator ...

3 people found this helpful.

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