i got a 95 Z28, lately ive been having trouble starting, it started a while ago, it would have to turn the engine a few times before it started and it would be rough for a few seconds. If i let it sit for 4 or 5 days it would be really hard to start and i would have to crank it for 20 or 30 seconds before it would start, my cousins a journeyman hd mechanic and he said it could be oil going back thru the filter, i changed the oil and filter and it seemed to work, for a few weeks. it then started doing it again. i also noticed that when im starting it the oil pressure guage would slowly go up to half way befor it would fire, thats what gave my cousin the filter idea, and it runs great and starts great after its been started and hasent sit for more thatn a few days. hes sayin the pressure sending unit may be screwed. has anyone else had this problem

thanks for the help

 

The F-Body does not have an interlock between the oil pressure switch and the starter circuit, so its not likely the oil pressure sending switch is causing the problem. The most common problem is rapid loss of fuel pressure when the pump shuts off after the initial prime. Put a fuel pressure gauge on the Schrade valve (hard line, behind the passenger side fuel rail) and turn the key to "on" without starting the engine. Pressure should jump to at least 40psi in the 2 seconds that the pump runs. When the pump stops, the pressure should stay close to that value, and not drop rapidly. If it does drop rapidly, it can extend starting times. Turning the key on and off several times in a row, then trying to start it may reduce the problem... and that would confirm the fuel pressure problem.

 

Thanks, good to know, lll have to try that next week when i see the car again,

 

I tried testing the pressure, as soon as i turned the key the pressure jumped to about 44 psi, then when the primer pump went off it dropped to 38 psi and holds it there and when i turn the engine over the needle stays at 38 - 40 psi

 

Doesn't sound like its a problem with the fuel pump. Pressures are normal.

 

ya i was hopin i would find the problem easy, gonna check the plugs, also whats an easy way to check the injectors to see if there working

 

To check the injectors, you need a "noid" light.... a small light that inserts between the harness connector and the injector, and flashed when the injector is pulsed.

http://www.sjdiscounttools.com/ta36330.html

 

Now im right lost, i checked the injectors with the noid light, i checked 4 of them, they all worked, i also checked 4 of the plugs for spark, they all worked, i could also smell fuel on the plugs so it must be getting fuel. i was thinking compression pressure, (what is it supposed to be) but i havent seen any evidence of burning oil, the exhaust has been clean up until it stopped working. also i replaced the head gasket 2 years ago, doesint seem like its leaking coolant into the engine, so im hoping nothing is wrong there. also what does the anti theft do, ive heard it shuts the injectors down, but they seem to be working, does it do some weird stuff or something

 

ttt

 

You indicate you smell fuel. May be flooding. Does it start easier if you hold the accel pedal to the floor BEFORE you turn the key to start, and hold it there while you try to start it?

 

Just tried that, it didint work. however it has been chugging sometimes after i release the key and i was reading a thread about another guy who it now seems like he was having the same problem, I didint finish the thread and now I cant find it again. When I release the clutch in first the car goes backwards when its chugging, I just replaced the starter, and it was fine when I replaced it, it would start up great and everything then it just quit working. I think I saw some posts from you (injuneer) in the thread, unfortunately the dates were 2008 or 2009 I think, so I dont know if you would remember cause I want to see if they found a solution to the problem. Ill keep looking for the thread hopefully I can find it

Also the car ran great up until it just decided it didint want to start anymore

 

found it, I was searching the wrong thing

 

Looking into everything, it looks like it is the opti, reading threads on here it makes sense, also I bought the car off my dad and he said that he had a very similar problem when the car was under warranty and it was the opti that time too (the opti is about 13 years old) I saw on here that you (injuneer) used a Electromotive SDI/Opti Eliminator on your car, how was that, cause if im replacing the opti i would rather spend more to go to a better system if it is better.

 

The Electromotive SDI/Opti-Eliminator hasn't been available for about 12 years. They only made about 20 units. They had "issues".

There's nothing wrong with the Opti. A high quality unit, properly installed, with the known required tweaks, will provide reliable service. If you want to pull the high voltage function out of the Opti, and rely only on the optical cam position sensor portion, look at the Bailey Engineering LTCC:

http://www.bailey-eng.com/LTCC.html

If you want to get rid of the Opti completely, and run on an LS1 PCM with 8 direct-fire coils, look here:

http://www.eficonnection.com/eficonnection/24x.aspx

You will require a high limit on your credit card.

But there is no reason you need those systems, unless you have a very high boost setup, running a huge shot of nitrous, or turning exceptionally high RPM.

 

Finally finished fixing it, took a long time cause I didint have much time to do it. Had to replace the water pump cause the bearings were shot, now I just have to figure out how to hook up the meziere pump to the electrical. looks like it was the opti, it fired up really nice once i got everything hooked up again, thanks for the help