Gravelguy413 Posted April 26, 2021 Share Posted April 26, 2021 Still having an Issue with full mechanical E7 fuel prime bleeding down over night and causing long crank times. Have replaced fuel return line and also lift pump no luck. Truck idles nice but seems to have a slight miss operating. Somebody earlier mentioned a possible bad injector. Would one bad injector cause long crank times? Also somebody mentioned a possible bad check valve. Where is this valve located? Quote Link to comment https://www.bigmacktrucks.com/topic/66603-fuel-prime-q/ Share on other sites More sharing options...
h67st Posted April 26, 2021 Share Posted April 26, 2021 The check valves are in the lift pump; if you replaced the whole pump that would fix them. My hand primer pump was bad, causing loss of prime but maybe you already replaced it. I found my leak by removing the lines at the fuel tank, plugging them off, and putting 10 psi air into them...fuel started seeping out of the primer so that showed where the problem was. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/66603-fuel-prime-q/#findComment-472973 Share on other sites More sharing options...
OldRedMack Posted April 28, 2021 Share Posted April 28, 2021 Check your fuel filter stand for cracks, took us 2 years to find that problem on a truck. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/66603-fuel-prime-q/#findComment-473077 Share on other sites More sharing options...
John3406 Posted April 29, 2021 Share Posted April 29, 2021 Should be a check valve in pump. I think its called an overflow valve. Should be up towards the top and side of pump but i cant remember without looking at the pump Quote Link to comment https://www.bigmacktrucks.com/topic/66603-fuel-prime-q/#findComment-473129 Share on other sites More sharing options...
MACKX Posted May 1, 2021 Share Posted May 1, 2021 If it’s a Bosch 7100 pump the overflow valve will cause extended crank times.... it’s on the top outside of the pump as John said earlier .... take it out and see if shakes like a rattle if it does it should be working ... you can take the end plug out and remove the spring and stretch it out to buy a little time before you get a new one if need be.... definitely check for air leaks also Quote Link to comment https://www.bigmacktrucks.com/topic/66603-fuel-prime-q/#findComment-473235 Share on other sites More sharing options...
Gravelguy413 Posted May 1, 2021 Author Share Posted May 1, 2021 Great thanks everybody Quote Link to comment https://www.bigmacktrucks.com/topic/66603-fuel-prime-q/#findComment-473260 Share on other sites More sharing options...
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