I know from the search that hard hot starting is really common on 103 engines. After my 93 TE 4-matic was smashed up last month I bought a 91 to replace it. Well needless to say the 91 is an absolute b!tch to start, especially hot. I spent some time today attempting to diagnose the problem.
The main symptom is that the engine will not attempt to start until about 10-20 seconds of starting. It's worst hot. It will restart ok for about a minute or two but any longer and the starter just spins and spins before anything happens. I had a faulty fuel accumulator and much to my disapointment replacing it didn't help the starting one bit. I noticed that the fuel distributor was leaking from the plunger so I replaced it with one of my spares, bumpkis. Didn't help either. So today I spent several hours after work trying to diagnose the problem. Here's what I know, the rest pressure is fine, as well as the system pressure. I watched the fuel pressure come up fine while the engine was refusing to start, so it's not pressure related. After failing to start I pulled a plug and it was dry, so it seems that there is a lack of fuel causing the problem. I pulled the injectors and bench tested them although it appeared that the previous owner had replaced them recently. Well despite being near new, they had a piss poor spray that cleaned up well on the tester. That didn't improve the starting but really helped on the low power problem that the car has been having. I did notice that that when I cracked the injector line loose there was a lot of vapor but no liquid fuel. That leads me to the conclusion that the system is actually vapor locking in the injector nozzles. It makes sense that the fuel dist will take a bit of time to purge the vapor out of the nozzles resulting in the delayed start. I noticed that there is an aluminum intake gasket on the engine, I assume from a previous head job. I'm thinking that this gasket may be the root of my problem. I believe that I should have the fiber gasket which would be a lot more of an insulator than the aluminum gasket. I am thinking that the excess heat being transferred into the intake is vapor locking the nozzles. If this proves to be the case then I may have stumbled onto something. I didn't chage it out yet but will certainly keep you guys posted with my results. I'm going to try a bunch of cold starts paying attention to how it responds, knowing now what I'm looking for. If I can get decent restarts before the engine heats up enough to vapor lock the injectors then I'm going to change the intake gasket. If I can duplicate the starting issue on a cold to warm engine that has run enough to prime the nozzles then I will have to dig some more.
07-16-2008, 12:14 AM
Linear Mode
