91 740 hot no start

[nisan17]

Hi Group,

This is a problem only occurring in the summer on hot days and when the car is driven for any length.
It is a 2.3 bosch ignition. When parked after any hot lengthy drive and sits for about fifteen minutes the car just won't crank, there is no hum from the fuel pumps. There is no click from relays or starter. Lights come on in the dash. So, we then play the waiting game. Ten minutes to as long as an hour the car will just crank like nothing happened.

Please, any ideas where to check? I perused the forum and came up with: Cold start injector, fuel pump relay, and radio suppression relay. Oh, I did change out the ignition switch with a used one.

Thanks in advance,

[lummert]

Have experienced this same problem many times with my 1988 Volvo 760 Turbo Wagon. If the temperature is high combined with low humidity the engine will act like the car has ran out of gas if the fuel tank level is not kept nearly full. I have replaced both fuel pumps but the same thing happened on Friday of this week. I had a friend take me to get a jug of gas, I put the gas in and it still would not start. Saturday morning it would start but idled very rough. I drove 1.1 miles to the station and filled the tank. After 2 trips to town the idle smoothed out and the engine was running good again.

The fuel in the tank had gotten hot and overheated the in-tank fuel pump, the pump then started pumping air and aerated the fuel in the fuel lines. After filling the tank with fuel time was needed to purge the lines and injectors of air bubbles.

First I would check the in-tank pump to make sure it hasn't died, the first sign of a dead in-tank pump is that the main pump under the car will be very noisy.

Keeping the fuel level at least 3/4 full will help with the overheating of the fuel.

I hope this will be a help to you as I have put up with this same problem every summer for the past 6 years.

One more thing, if the in-tank pump has died it will shorten the life of the main pump as it was not designed to pull fuel from the tank. The in-tank pump is a low pressure, high volume lift pump that is supposed to supply the fuel to the main low volume, high pressure pump.