All of a sudden, the car has become difficult to start after sitting for more than 4-5 hours. You have to crank and pump the throttle to get her started ...

I've checked the fuel pump (runs when the key is turned for a few seconds and then shuts off); the fuel pressure is fine (40+lb/in2 and sees to hold when the the key is off), and I have a spark (the strobe light lights up fine).

The engine was completely rebuilt 18 months ago, and all sensors are new, as are the injectors.

I did search the archives and couldn't come up with anything that seemed to fit ...

Given the need to open the throttle wide to start her (and even then it she struggles) I am wondering if it is a leaking injector problem.

I will do a longer fuel rail pressure test to see there is a decline over time (how long should it hold pressure?): if it doesn't then I'm guessing that the FleaBay Ford EVO injectors are junk!

In the meantime, I'll post the above just in case there is something else I should be looking at!

Thanks, ATG

 

Verify you have strong consistent spark while starting. Optispark issues can sometimes be first noticed as hard cold starts that do not throw diagnostic codes.

 

the WOT sounds like it is too rich. maybe injector, CTS. if it starts and sputters for a few seconds, may be due to the wet plugs.

 

Certainly have enough to light the timing light. Did take out a plug and was getting a spark ... didn't look too strong so I tested the output with a Snapon KV meter, which tells me I'm getting 10kV at the plug when she is running. Tried a number of plug leads, and all were about the same reading.

I did a longer fuel pressure test, and the rail held 43lb/in2 for about an hour with a very small decrease (and that might be because of the poor pressure gauge fittings).

Also, did a NOID light test and the injectors are lighting up the test plug.

That's what I thought too ... but she doesn't start and die, or splutter for that matter, just turns over faster and faster before limping into life. Also, the plug that was taken out was removed after an extended period of cranking with no throttle and it was dry.

I'm suspecting that it is fuel related but will do an ether Easy Start spray test tomorrow to see if she fires immediately.

I'll report back tomorrow and let all interested know what I have found out!

 

OK. Just in case anyone else has the same problem!

Since once the car was started, she would generally start easily, so I had to wait until the next day to see if she would then start with Easystart ... nothing. Tried a couple of times with more squirts with the throttle bodies open, and so ruled out fuel shortage.

So it is ignition related. Bought a GM replacement coil, and once replaced, she fired first turn, and has run fine since.

I had come across a lot of mentions of MSD coils failing on the F-Body sites: well, this is another one ... I bought the high end MSD-8226 high output coil. Obviously a heap of sh*t. All those folks who said stick to GM coils knew what they were talking about. Incidentally, I tested the new working coil with the kV meter, it is reads about 13-14kV ... about twice that of the old unit that had failed was reading once I got the engine running with the old coil.

Appreciate all the suggestions made, but must say that I found the LS1/LT1 forum a great site (http://www.ls1lt1.com) for trouble shooting the issue, and that led me to the SHBox site (http://shbox.com) which helped me nail down the problems. Those F-body gearheads really know their LT1s, thank goodness!

The one thing that still baffles me is the fact that this was a cold start problem ... all I can surmise is that the voltage drop to the coil as a result of cranking was insufficient for the coil to generate a spark, and when cranking at WOT she was able to reach high enough crank speed to catch one or two cylinders and then limp into action(I know that WOT affects the FPR, but don't know if that would have affected the outcome ...).

 

interesting info.

the WOT affects the fuel supply at injectors, basically turned off, at 20:1 AFR. thus the WOT to clear a flood.

the 10kv is probably the best clue here, as fsm tester requires 20kv to spark it. "spark" and enuff' spark are not the same.

no/slow start cold due to coil is still a mystery, for me.

saludos,
joe

 

Just wanted to add a post-script to the tale. It ended up not being the coil after all (wish I had known that before I had pitched the original EXPENSIVE MSD unit!).

The new coil ran for a few days, and then the car died on the interstate when accelerating hard (not sure it is relevant, but it might be!).

Flat-bedded home (2 miles thankfully). After going through the FSM diagnostics for the 94 (and missing reading a YES NO leg ... which ended up with me changing the Optispark for no good reason ... and the car still not starting), I re-check the FSM steps and it pointed to a faulty ignition module. Once replaced, the car is running fine once more.

It is clear that the IM can present cold start faults ... I just wish I had followed the FSM tree (in book 2 Driveability Issues) when it first happened ... it would have saved me pitching a good coil and all that followed. Note to self: do not assume that what you are convinced is the problem IS the problem: check twice before fixing something that is working fine!

 

Old thread, but it helped me out.

My 94 6spd had all the same symptoms.
On a cold morning, the car required foot to the floor to start, then idled like an over-cammed funny car until it warmed up. I watched the avg mpg drop by the second while it dumped fuel out the exhaust.

Of course the water temp read Lo at startup, but when the car sputtered while driving, I caught the displayed temp jumping from normal operating temperature to “Lo” and then back.

That was my hard clue that the sensor on the wp was bad. As this was a new one that came with the new wp, I discounted it at first.
Plenty of great info on the forum about the effects and pervasiveness of a bad water temp sensor.

Swapped out for new, runs great. A real gremlin, but now I know.