This is weird. If I try to start my Blazer by turning the key normally,it doesn't want to start . I have to try several times. If I turn the key fast like snatching it, it cranks right away first time. Idles fine. When I accelerate , it stutters and hesitates really bad. If I really get on it, It almost wants to cut off, Especially if I power brake. I've changed fuel filter,plugs,and rotor button.Previous owner changed fuel pump,plug wires and cap. Says they have about 9k on them. But said when he checked pressure he was only getting about 10 psi. My question is could this be causing all my problems or does it sound like an ignition problem as well? Bad distributor and pump? When I cruise, It runs fine, only when under load does it sputter and sounds like all 6 cylinders aren't firing. Any Ideas? Thanks in advance!! By the way - no codes all checks fine - code 12

 

Sounds like a fuel pressure issue to me. I am not sure what the psi is supposed to be on the TBI, but I am sure it should be more then 10. Was the filter plugged bad when you changed it? A severely plugged fuel filter can kill a pump.

I would also look into the fuel pressure regulator.

 

Filter was not plugged bad. Had some black stuff come out when I knocked it on a table. TBI was taken off and completely cleaned, injectors cleaned professionally, fuel pressure regulator rebuilt . All this done by ASE technician who previously owned the truck. Checked all sensors - good. He said it ran fine for about 8k miles after he changed fuel pump (from Advance) . Only sputtered a little bit under load. Maybe a cheap weak pump?? Or maybe not getting correct voltage - I don't know.

 

Did you try to blow through the filter at all? That is how I test them out. If I can blow through it in the flow direction easily, it isn't that bad. If I have a hard time getting any air though it, it is very bad and could damage the pump.


I would check to see what the fuel pressure is supposed to be at and go from there. Might have to call a dealer if you can't find it on here or in a book ( if you have one )

 

yes i did the blow test. easily blowed out fuel. I'll check to see what my fuel pressure is suppose to be but i think it suppose to be around 16psi on tbi but not sure.

 

8-10psi for TBI so that part sounds good.

Almost sounds like a timing problem. Have you verified the timing?

 

Yes timing was off when I purchased the vehicle. It was at 6 degrees. Checked Haynes manual and it said it needs to be set at 0. So I set it at 0. (with the timing wire underneath passenger floor disconnected)I'm wondering if it could be the coil or the distributor itself. Cap,wires and rotor are new. Distributor looks rusty underneath cap. Truck cruises along good when up to speed. Would'nt a timing or ignition problem make it run rough all the time and not just under load?

 

Not necessarily. Timing will change with load. In pre-computer controlled distributors, this was accomplished with the vacuum advance in combination with mechanical advance. The vacuum advance was based on the engine load as a function of manifold pressure. Mechanical advance was a function of RPM and modified via weights and springs.

 

Ok , that's over my head. Thanks for the info. Do you have any suggestions on what I should check? I thought it could have been fuel pressure but since you said 10psi should be good, I now think it must be an issue with firing and misfiring. I did set the timing, but could it be off again? Maybe computer? But i am getting code 12 and that's it. I'm stumped and almost to the point of just replacing the distributor and coil but that wouldn't be very economical! I really don't have time to take to a mechanic because I drive this truck daily.Any ideas and help is greatlly appreciated! Thanks. Maybe I should pull the distributor and check for a worn gear. I've read about this in other posts.

 

I unplugged the #4 and #6 plug wire and the engine didn't run any different! Tha's not good! Anyway,in a hurry,I plugged the wires back in crossed. Drove about 4 miles - ran terrible- knew exactly what was wrong. pulled out Haynes manual and routed plug wires correctly. Unplugged battery for a few minutes to reset any codes. Now truck will not start at all. Did I cause any damage?