Very slow to turn over on start - What's the likely culprit
03-09-2012, 12:08 AM
#17
Rennlist Member
Scott, when I said that I thought it was fuel, I didn't mean bad fuel, literally. What I meant was that any engine needs air, fuel and spark-- in the right proportions-- to run properly. I suspect a problem with the fuel delivery to the engine.
If it cranks OK but is reluctant to start, then it could be too much fuel (i.e. flooded) or too little. With too little it will usually start and run, badly. With too much fuel it will only start with lots of extra air, i.e. open the throttle as you described in your first post.
One good test is to crank the engine (throttle closed) for 10 seconds or so, then (if it doesn't start) pull a few spark plugs. If they are wet with fuel (identified visually and with the sniff test) then it is too much fuel and the engine is flooding. Also, sniff the exhaust after cranking-- does it smell like fuel?
There can be many causes for too much fuel: MAF (happened to us), temp-II sensor (engine thinks it is very cold when it isn't), damper/regulator leak as noted above, etc.
A clogged filter or injector would be too little fuel-- dry plugs after cranking, no fuel smell in the exhaust.
Engines are complex things, and problems can have many causes. The only way to diagnose it and remain sane is by being methodical... Make a list of possibilities and then start crossing them off.
The WSM is a big help, if you don't have a copy then stop and get one-- Paper, CD, download, doesn't matter. There is a good section on troubleshooting the fuel injection section, how to check each sensor.
And folks here can be a great help, but you need to provide more details: History of the car, what's been done, what hasn't, and (especially) what was changed just before the problem started.
Good hunting!
If it cranks OK but is reluctant to start, then it could be too much fuel (i.e. flooded) or too little. With too little it will usually start and run, badly. With too much fuel it will only start with lots of extra air, i.e. open the throttle as you described in your first post.
One good test is to crank the engine (throttle closed) for 10 seconds or so, then (if it doesn't start) pull a few spark plugs. If they are wet with fuel (identified visually and with the sniff test) then it is too much fuel and the engine is flooding. Also, sniff the exhaust after cranking-- does it smell like fuel?
There can be many causes for too much fuel: MAF (happened to us), temp-II sensor (engine thinks it is very cold when it isn't), damper/regulator leak as noted above, etc.
A clogged filter or injector would be too little fuel-- dry plugs after cranking, no fuel smell in the exhaust.
Engines are complex things, and problems can have many causes. The only way to diagnose it and remain sane is by being methodical... Make a list of possibilities and then start crossing them off.
The WSM is a big help, if you don't have a copy then stop and get one-- Paper, CD, download, doesn't matter. There is a good section on troubleshooting the fuel injection section, how to check each sensor.
And folks here can be a great help, but you need to provide more details: History of the car, what's been done, what hasn't, and (especially) what was changed just before the problem started.
Good hunting!
