Brief History: Car was parked 4 years ago in perfect running condition. Over last couple years just starting it to move it around started experiencing high temperature spikes after short periods of time. Shipped to mechanic, diagnosed with head gasket, the head gasket was replaced and all fluids changed and radiator flushed. I drove the car 200 miles from PA to OH with no issues.

Problem 1: After about a week I started noticing slight temperature spikes while idling (sitting). During normal driving the car is around 180-200. When at stop signs etc... the car will spike to about 210-235 for a few minutes then settle back to around 200. This makes me assume that it might be coolant flow issues but I am not familiar with these engines.

Problem 2: The oil pressure seemed fine about the first (2) weeks but lately its been running around 40 psig under load and at idle around 20 psig. I am not sure if that is low or normal but it seems lower than what it original ran at.

Problem 3: This is a real strange one. The mechanic said it ran fine before I picked it up but the only issue was that when he refueled the car it would not start after. He stated he replaced the fuel filter and it was fine. Well the last two times I have refueled I have found my self stranded at the pump. The car run fines. I pull into the pump and fill it full. I go to start it and it will turn over but it stalls shortly after. Things I noted was the "Low Oil" light will flash briefly and then the "Air Bag" light will flash 6 times then stop. My short fix is I go out pull on the throttle cable a few times while the car is off and then it seems to start up fine after and then it continues to run fine until next fuel stop.

Any help would be appreciated

 

Oil pressure seems fine, but hook up a mechanical gauge to confirm the dash readings.

Sounds like you have air in the cooling system, re bleed and see if that fixes it.

The last one, that's weird. Hook up a fuel pressure gauge and see what that's doing after a fill up. Does it only do it if you top it off? Or if you add any amount of fuel?

 

Stock fan temps are 224 for low and 236 for high if I remember correctly. These cars will yo-yo between the 1/2 and 3/4 marks on the gauge when idling. Doesn't sound like your mechanic is familiar with these motors and changed the head gaskets for no reason.

Your oil pressure is fine. If anything, it's healthier than most. Usually they sit around 15-20 psi @ hot idle and under 40 cruising around.

+1 on checking the fuel pump.
Are you overfilling the gas tank? I wonder if the EVAP system could be pulling in raw fuel.

 

The temperature as described was how it is now. Before the head gasket was replaced it would be in the "Red" (i.e. 255-260) within a few minutes of start up, there was definitely an issue although I personally feel it was the water pump (which was replaced as well) I live 4 hrs. from the car so I had to trust his judgement. Now that its out here I will never let another mechanic unfamiliar with the engine platform work on it.

So if I interpret what your saying right, then 210-225 is normal and perfectly fine at idle?

My only concern with the oil pressure was that I am normally at around 40 psig while idling and between 50-60 under load. I would offer today it seemed to work fine again though.

Might be naïve but how does one check the fuel pump on an LT1 as again I have no experience working on these engines but am trying to learn. If the fuel pump was not operating though would I be able to get it started at all?

PS. I like the SS Spoiler on your car very clean looking.

 

I have only filled twice but am about the 1/4 mark when I fill and I pump till its full and the gas pump stops. Where would I be hooking the pressure gauge at?

Also do you have any tutorials on bleeding the LT1 cooling system?

 

Anyone have any insight on the Dash readings (i.e. Air Bag Light) is that like a code sequence for diagnostics?

Edit: Could it be a ground problem? Are any of the electronics related to the fuel system associated with the same ground?

I noted the ground was suspect in both these situations.

https://ls1tech.com/forums/lt1-lt4-m...bag-light.html

http://www.ls1lt1.com/forum/car-audi...light-off.html

 

Next time you fill up, don't top off; go to 3/4. If the condition doesn't happen, look at the EVAP system.

On the back of the engine just behind the intake manifold you'll see a Schrader valve. Hook up a fuel pressure gauge there. You'll want to check fuel pressure with key on engine off. Then check it with the engine idling, then check it while driving if you can. Also check it again after you turn the engine off, key off.

To bleed the coolant, open your radiator cap. Then open both bleed screws (one on the thermostat housing and one on the heater house in front of the alternator), fill the radiator until only coolant is coming out of both screws. Then close the screws, start the engine and let it warm up until the thermostat is open, add coolant to the radiator as necessary. Cap off the radiator once full. Fill the over flow reservoir, turn off the engine and let cool completely. Once cool, open radiator cap and fill as necessary. Check again after your next drive cycle.

 

I've had to drain coolant and refill and bleed. There is a special procedure on shbox.com showing where the bleed valves are. My car did the same thing yours did with temp at first, but I bled it well and had it custom dyno tuned and the fan temps were changed. It barely goes over the first quarter now in 100 degree weather.

My car has an occasional hard starting issue as well and I think it may have something to do with the EVAP code. It let's out air each time I crack open the gas cap, so I know it isn't venting. Do you have an EVAP code?

As far as oil pressure goes, that is perfectly normal based on what my car shows. Most of the gauges seem to be off on the early fourth gen cars. The speedo is slow, tach was off 400rpm compared to the dyno, and the oil pressure gauge seems useless.

 

[QUOTE=hrcslam;18960903]Next time you fill up, don't top off; go to 3/4. If the condition doesn't happen, look at the EVAP system.
QUOTE]

I only filled it to approximately 3/4 this time and the car started up with no issues. From your prognosis it sounds like something in the EVAP system but what specifically should I be looking for?

 

Yes. That's likely. The fuel system on our cars is a return style. So the pump will pull fuel from the bottom of the tank, pump it to the injector rails, then through the FPR, and back to the tank. Then there's the EVAP system. That takes the vapor gases from the tank, stores them in a charcoal canister (located behind the fill port in the drivers 1/4 panel), there's a vacuum line that runs from the canister with the fuel lines to the engine. The vacuum line comes out of the fuel line harness above the drivers valve cover, routes under the TB to the passenger side of the intake to a solenoid, then from the solenoid to the intake manifold via a small vacuum line.

My next step would be to disconnect the vacuum line from the solenoid to the intake manifold and plug it off. Check the solenoid side for raw fuel (after top off), it should be vapor only. With it blocked off, top off the car and see if the hard start continues. If it does the condition is caused by something else, if not you found the issue.

It sounds like the top off is allowing fuel to overflow into the charcoal canister and over fuel the engine due to too much fuel in the intake plenum.

That's my guess. Good luck.