tom3

When I got my car I noticed it always took 6 or 8 revs before the engine would fire. Now, years later it's more like 10. This engine has pretty good compression and in recent cold, real cold, weather that's hard on the battery I think. I read somewhere years ago the ECM has to see 8 revs before it turns on the injectors. But the other day I read that the ECM actually reads oil pressure, 3 or 4 psi and it starts the injectors. Kind of makes sense as when my car turns over faster, it starts sooner seems like. Anyone know how this actually works? Could I put a push button switch with a resistor in the oil pressure circuit to "fool" the ECM, give it a pressure reading that would get the fuel flowing quicker? Does the ECM read the same sensor that the gauge uses? Any ideas?

riphc06

I think we all hate that problem. I'm not sure how the system works, but if it is the case that it reads oil pressure, I would say its a good thing. It makes sense after all, considering it will start right up when the engine is warm. I guess its just a failsafe for the engine to make sure you get some oil in the bearings before it starts firing. Think of how you have to prime the oil pump through the distributor hole on a new engine. Personally, I would not trick the ECM into thinking there is oil pressure if there is'nt. You may want to go the direction of finding a way to maintain oil pressure.....seals, etc. Hope this helps.

riphc06

Maybe I'm nuts but one thing I always do on cold starts is turn the key to run/on to let the fuel pump prime, then off. Wait about 20-30 seconds and do it again, then start. It seems to help with the long start problem. Good luck!

vetteoz

iTrader: (13)

Long crank ,hard start is commonly related to losing fuel pressure.
The ECM runs the pump for 2 sec to pressurise the rail then turns off.When cranking ,once the OP is above 4 psi the oil pressure switch turns the pump on.If you lose rail pressure after the pump primes , you have to wait for engine oil pressure to go above 4 psi before you get rail pressure back.
Could be bad fuel regulator , bad check valve in tank or leaking injectors for starters

ECM does not read OP directly.
While cranking if it sees the oil pressure switch come online (OP above 4 psi ) and power the pump up and also sees the reference signal from the dist then it will allow the injectors to pulse
Read
http://www.corvettebuyers.com/c4vettes/l98.htm