Discussion
Hi all.
I'm looking for a bit of advice really.
I have a Mk1 Escort with a 2.0 Zetce engine with jenvey throttle bodies, mbe stand alone ECU. Rickwood cnc head +30 thou.
Anyway I took it for a spin yesterday and was running good. After about 50 mikes I stopped to fill up. On trying to start the car it failed to start. I didn't turn it over much as I was scared of flattening the battery. I left it 15 minuites and it started first time. I maybe didn't try for long enough on the first occasion I'm not sure now. Any idea what's going on? It's always starts well from cold BTW.
I'm looking for a bit of advice really.
I have a Mk1 Escort with a 2.0 Zetce engine with jenvey throttle bodies, mbe stand alone ECU. Rickwood cnc head +30 thou.
Anyway I took it for a spin yesterday and was running good. After about 50 mikes I stopped to fill up. On trying to start the car it failed to start. I didn't turn it over much as I was scared of flattening the battery. I left it 15 minuites and it started first time. I maybe didn't try for long enough on the first occasion I'm not sure now. Any idea what's going on? It's always starts well from cold BTW.
Assuming something hasn't broken then it'll be poor mapping. IME, most aftermarket ecus are mapped very badly when it comes to starting across a range of temperatures, battery voltages, fuel grades, coolant temps etc etc (Simply because it takes hours, and hours of mapping to do it properly!)
Starting mapping is always more difficult than running mapping, because you can't trust any AFT gauge, and because being too rich is just as bad as being too lean! Any issues with poor position sensing (crank/cam etc) also tend to show, and can lead to synchronisation failures etc
I'd carry out some basic checks (fuel pressure, compression, cam timing, spark dwell etc) and then try to get some data logs of the starting to determine what's going on!
Starting mapping is always more difficult than running mapping, because you can't trust any AFT gauge, and because being too rich is just as bad as being too lean! Any issues with poor position sensing (crank/cam etc) also tend to show, and can lead to synchronisation failures etc
I'd carry out some basic checks (fuel pressure, compression, cam timing, spark dwell etc) and then try to get some data logs of the starting to determine what's going on!
PS. As the ems is a pretty simple one, there won't be many fuel correction tables. So i might be worth posting up those tables for people to look at and advise. I often see warm start fuelling tables where the mapper has continued to reduce the pre start fuel trims with increasing water temperature, whereas you really always need a significant "first pulse" to ensure you fill the manifold puddle mass immediately (to prevent a lean excursion just when the engine is trying to run up, and there is a large dynamic pressure decrease in the manifold. On a warm start, because you have less wall condensation, you don't need to continue to add too much extra fuel (unlike of a cold start) but you do need enough in immediately to ensure the puddle mass has formed. Most aftermarket eucs use basic fuel trims based on coolant temperature and temperature at crank, and generally ramp the fueling off against firing cycles. So you probably want quite a bit extra fuel on crank, then ramp it out rapidly against running cycles, leaving just a small coolant temp based correction depending on the actual coolant temp
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