GM LT1 Starting issue & Temp Sensor (here we go again...)

Well, after a couple weeks of great service, the car has started not starting again. It hasn't stalled, but it's taking a while to start it. Once it starts it's running GREAT.

Running through some options with a friend of mine who knows cars, I cranked it over the phone and he said it cranks fine, but *it is not getting enough fuel to start*, then we ran through what was done with it recently, engine-wise:

It's had a fuel induction system cleaning, new plugs and wires, and all the major fuel system services done in August of 2010. That was about 6000 miles ago.

Then, the check engine light came on, and I got the code out of 00 on the diagnostic system: 15. Coolant temp sensor (low temp).

Now, I'd been watching the coolant temp sensor readout before the check engine light came on (24 on the diagnostic system) and it took a while for the thing to change from 00, and occasionally it jumped around.

Any ideas? I'm not sure where to go from here, the wiring for the temp sensor goes into the wiring harnass and under the air intake, so that'll be a real bitch to get to.

I'm broke after putting Monroe Severe Service shocks on it, which are a bit stiff, but overally great, so I can't afford to take it to a real mechanic

fuel pump

I've had 3 go bad on 3 cars. How many miles on the car? Over 150K I'm betting my lunch money on that, or the damn little rubber hose between the pump and the sending unit. Either way you are dropping the tank.

see here for details:

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IF it is the pump, I have a used one (that ran fine 5 years ago when I got it) you can have for the cost of shipping. Sending unit comes with it, but it also is of unknown accuracy.

87k original miles. I know you have to drop the tank....and I do not relish the thought of doing that

Offer much appreciated...I'll have to see if I have any local friends that might be able to help me.

easiest way to check is to go to your local parts store and borrow a fuel pressure tester. just screws onto the schraeder valve on the fuel rail. My car ran fine for YEARS with around 25psi and I didn't even know. Car runs MUCH better with new pump at 40psi.

i went through this in the fall with someone elses truck. the truck would have to turn over many many times to get it to start. once it was warmed up and running it seemed to work great. as time went by the issue got progressively worse. it got to the point where we would have to prime it (pour some gas down the intake) in order to get the truck started. i had a good feeling it was likely the fuel pump even though it was replaced recently that same year. when we did finally put a new fuel pump in, the starting issue stopped and we noticed a BIG difference in performance.

Try this put the pedal to the floor and try starting it. I had the temp sensor in the pump go bad and was reading -40 degrees and flooding the car once I opened the t/b up I had enough air to get it to run

Also from what I have been told the car has 2 sensors, one for the gauge and one for the ecm

That's the thing....I looked at the output and it read out 40ish, most recent trip it read out 61 and stayed there (which is when the light came on).

I replaced the temp sensor in the pump and cleaned the connector thoroughly. Which is what leads me to believe that there's a short somewhere in the wiring between connector and computer. I'll ohm it out tomorrow.

Temp sensor still reads out 61.....after a bit of cranking the car now does this all the time:

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I recorded it. I figured that would be the best way to describe what is happening.

Now I'm not sure how I am going to get my new sensor since I can't limp this thing up to AutoZone.

aaaand another update. Went to AutoZone, bought another sensor, pulled the connector off the old one, plugged new one in...reading changed. Put new one in, reconnected: reading went back to 61....messed around with wiggling the connector on the old one, no change, plugged back into the new one...all good.

So I guess the duracrap sensor was bad and the wiring's funky. I'll replace the pigtail and connector once I go back to AutoZone and return the bad sensor.

BUT. The car now starts better than my mother's '05 Chevy Classic! The Roadie seems to be running great. When I go back to AZ I'll see if I can borrow/rent a fuel pressure checker and see if someone'll help me check the pressure to see if I have to replace the fuel pump, because I'll do it if it needs it.

Sounds like you got it, but do still check the fuel pressure. Easy one person job, hook it up, key on and take a look. Better to find out now if the pump is dying then to find out far from home.

if the pump goes it's usually all of a sudden. the split rubber is a slower death (you can limp the car slowly). When the FP went in my '94 it was as simple as pull into walgreens parking lot, then try to start it 2 hours later (dropped car off and left with someone else) and no start period. That was around 175K, so I figured it had a good run.

Hey im new to this forum. I have a 94 caprice wagon. I'm having a similar problem with my wagon. It only starts when i hold the gas in WOT. But it does that everytime i shut it off and when cold misses terribly until i rev it out a few times, the runs fine. I replaced the temp sensor and it made no difference. I also get no temp gauge reading, its always pegged to cold. The sensor wire by the header was broken down near where it enters the loom and i re attached it but still nothing. Checked all the other sensors, everything checked out fine. Im thinking maybe FPR or pump check valve? Thoughts? Thanks guys.

Probably another break somewhere down the wire...does your caprice have the digital temperature control unit? If it does, hold down off and temp up for a bit, you'll get into service mode. Scroll with the fan control buttons to #24 and see if you get a reading.

Wow,listen to you David already diagnosing problems for newer members!How goes the body
repair?
Jim

vinyldavid wrote:

Probably another break somewhere down the wire...does your caprice have the digital temperature control unit? If it does, hold down off and temp up for a bit, you'll get into service mode. Scroll with the fan control buttons to #24 and see if you get a reading.

Only the roadmasters have the diagnostic mode.