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Topic: 1981 Engine Oil Temp Too Hot??

in Forum: C3 Q&A with Dave McLellan


1981 Engine Oil Temp Too Hot??

Posted: 6/19/11 9:38am Message 1 of 17
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Stanley, NC - USA
Joined: 8/9/2010
Posts: 91
Vette(s): 1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box
    Facts are I have a 1981 Corvette, stock (Jasper) engine, all emission, AC etc compontents are in engine compartment and working. I have been having a loss of fuel to carb at times when running on the road, stopping engine for about 5 minutes, refire engine, starts up but then stops and no fuel to carb. Entire fuel system has been gone thru, new AC Delco manual fuel pump installed.
    Yesterday while testing car, ran 27 miles in mid 80s degree temps, I noticed engine oil temp was at 240/f on gauge. Water temp was 180/f and oil pressure was 60-80.
     Back at shop, shut off engine, waited and refired engine in 5 minutes, same thing happened, engine shut down and no fuel to carb.
     Using IR temp gauge recorded 204/f at top of fuel pump where connects to block, 174/f at bottom of bowl on fuel pump.
     Once car cools down, can spin engine, pump gas several times and she will refire.
     Can it be that engine oil temp is so high that heat is transferring to fuel pump and causing it to vapor lock or whatever to not pump fuel to carb?
     I cannot say on past times this has happened what oil temp was for I mainly monitored the oil pressure and water temp while driving. But the several times this loss of fuel has occurred the air temp has been 70/f and higher, never had problem when air temp has been cooler. Again this does not happen every time, so also can oil temp be running hotter at times and cooler at other times?



Tommy
 
   
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1981 Engine Oil Temp Too Hot??

Posted: 6/19/11 10:34am Message 2 of 17
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Red Lion, PA - USA
Joined: 10/27/2006
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Vette(s): 1974 White 350 Corvette, TH400 Automatic 1972 Tangerine /Go Mango Convertible 383 Stroker, 2004r Automatic
Tom, just looking to get some additional information. When you say you have no fuel to carb, are you looking in the carb for spray or have you removed to line going into the carb?
Rodney




1981 Engine Oil Temp Too Hot??

Posted: 6/19/11 2:54pm Message 3 of 17
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Stanley, NC - USA
Joined: 8/9/2010
Posts: 91
Vette(s): 1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box
    The answer to your question is yes to both, no fuel from jets in carb and no fuel from line from fuel pump when disconnected. Fuel supply from tank is okay.
     Fuel tank has been drained, cleaned and new pickup sock screen installed. Both line between tank and fuel tank blown out, new AC Delco fuel pump, new "S" hose, new line from fuel pump to carb and new (rebuilt) Rodchester carb. And new fuel cap now.
    Again when it gets hot and engine is stopped for a short time, refires but then runs out of fuel and no fuel to carb. Can do nothing and let car cool down and spin engine, pumping gas and she will refire and run then. So thinking is it is a heat related issue but heat from what? Again I did observe engine oil temp to be 240 yesterday and was 85'ish outside temp. We tested fuel retrun line yesterday after re-firing and had fuel flowing back to tank, not a steady stream, was a little burp or two while pumping back to tank.



Tommy
 
   

1981 Engine Oil Temp Too Hot??

Posted: 6/19/11 5:51pm Message 4 of 17
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HOWELL, NJ - USA
Joined: 5/18/2004
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Vette(s): 1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.
Is  it possible that the rubber S hose is collapsing due to the heat?


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1981 Engine Oil Temp Too Hot??

Posted: 6/19/11 6:50pm Message 5 of 17
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Sounds like a classic case of vapor lock. Hard to believe, considering the quality & volatility of the fuels available these days, but it sure sounds like that is what is going on. You've pretty well eliminated everything in the fuel system now...except the fuel itself.
My only suggestion now would be to try to insulate the fuel line from the carb to the pump. The fuel pump could indeed be getting overheated from the oil temp, but...your oil temp seems to be reading waaaay higher than the water temp....that's not normal. Oil temps should be just a little higher, in most cases, than the coolant temp.



Joel Adams
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1981 Engine Oil Temp Too Hot??

Posted: 6/20/11 5:37am Message 6 of 17
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Stanley, NC - USA
Joined: 8/9/2010
Posts: 91
Vette(s): 1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box
  Already had heat wrap tape on the new line from the fuel pump to the carb and did not stop the problem. We removed it since not only would it prevent heat rise it may also not allow for air flow across it to cool it back down. We put everything back to orginial set up to try and better ID the problem.

    On the oil temp higher than the water temp, I too thought that was a wide gap. I am unsure of how the oil temp has been in the past for I rarely looked at it, really monitored the water temp and oil pressure. Car is still at Corvette Etc in Charlotte so I cannot take it back out now and check oil temp right now but that is one item I will monitor in future and see if oil temp is varying at times and when it is at 240/f I lose fuel to carb.

   As far as the "S" hose we have put a new one on the car and have checked it to ensure it is not sucking shut when hot or when we lose fuel.



Tommy
 
   

1981 Engine Oil Temp Too Hot??

Posted: 6/20/11 8:06am Message 7 of 17
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Tucson, AZ - USA
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Vette(s): 1970 White L-46 Air Roadster, 1971 White LT1 Coupe, 1971 Red Auto Air Coupe, 383 stroker, 430 HP, 2002 Millennium Yellow Auto Coupe
[QUOTE=Adams' Apple]Sounds like a classic case of vapor lock. Hard to believe, considering the quality & volatility of the fuels available these days, but it sure sounds like that is what is going on. You've pretty well eliminated everything in the fuel system now...except the fuel itself.
My only suggestion now would be to try to insulate the fuel line from the carb to the pump. The fuel pump could indeed be getting overheated from the oil temp, but...your oil temp seems to be reading waaaay higher than the water temp....that's not normal. Oil temps should be just a little higher, in most cases, than the coolant temp.
[/QUOTE]
 
Time for a compression test? Blowby from the top of the cylinders can get into the crankcase and cause very high oil temps. Just a thought.




1981 Engine Oil Temp Too Hot??

Posted: 6/20/11 10:26am Message 8 of 17
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
You'll think I've lost my marble(yes, I said marble), but get some of the old-style, wooden clothes pins, and clamp as many as you can on the fuel line from the pump to the carb...see if that helps. If it IS vapor lock, that will solve it, or at least confirm it. It may look stoopid, but, I promise it will work, IF it is vapor lock......


Joel Adams
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1981 Engine Oil Temp Too Hot??

Posted: 6/20/11 11:38am Message 9 of 17
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Former Member
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Stanley, NC - USA
Joined: 8/9/2010
Posts: 91
Vette(s): 1981, dark blue w/carmel interior. 350 stock, auto tranny, Q-jet carb, ECM box
Mechanic called me a bit ago, appears a problem is in the fuel pump's push rod and possible cam lobe......if so can we say "headache # 101"?


Tommy
 
   

1981 Engine Oil Temp Too Hot??

Posted: 6/20/11 7:49pm Message 10 of 17
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
I can!!
Can't see the correlation tho, between a worn cam/pushrod, and the running out of fuel when hot only issue....unless it is simply a loss of fuel pressure that allows the fuel to vapor lock.
Chances are, IF the end of the pushrod is worn enough to see any wear, the cam lobe is also worn. Only two options at this point....change the cam & pushrod, or...electric fuel pump. Guess which one I would be doing?


Joel Adams
C3VR Lifetime Member #56    

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(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

in Forum: C3 Q&A with Dave McLellan


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