Diagnosing a hard start
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Diagnosing a hard start
1989 F250' 5.8 4x4 single cab.
Engine turns over fine, once started it runs as normal. I did a bunch of work over the summer and the truck while it has been a nickel and dime battle has never left me stranded . I finally purchased a new truck and this is now my beater and primary plow truck. Just starting the other day after it sat about 5weeks (started a couple times to move it) it suddenly took 30 seconds or so of off and on cranking to get it going. Hooked up the pressure guage , getting 35 or so when I turn the key but don't crank, at crank it hovers 30-35. Once it starts pressure hovers at 30 and takes several minutes to leak down after I shut it off. In tank pump was replace this summer, pressure pump on the rail was replaced a few years ago. Back tank has a new pump but leaks so I don't use it. I did also replace the fpr this summer. Any ideas on what to mess with next. I am just afraid we will get our first snow and it won't start which would suck.
Thanks,
Z
Engine turns over fine, once started it runs as normal. I did a bunch of work over the summer and the truck while it has been a nickel and dime battle has never left me stranded . I finally purchased a new truck and this is now my beater and primary plow truck. Just starting the other day after it sat about 5weeks (started a couple times to move it) it suddenly took 30 seconds or so of off and on cranking to get it going. Hooked up the pressure guage , getting 35 or so when I turn the key but don't crank, at crank it hovers 30-35. Once it starts pressure hovers at 30 and takes several minutes to leak down after I shut it off. In tank pump was replace this summer, pressure pump on the rail was replaced a few years ago. Back tank has a new pump but leaks so I don't use it. I did also replace the fpr this summer. Any ideas on what to mess with next. I am just afraid we will get our first snow and it won't start which would suck.
Thanks,
Z
Fleet Owner
Joined: Aug 2005
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From: Easton,Ks
The 30psi sounds normal at idle with good vacuum.
The other pressures you listed do not mean much as there is no reference at those operations.
A brief WOT should be about 40psi or grounding pin #6 of the self-test plug at KOEO would also be 40psi.
Does it start right back up after it has ran and then cooled a bit? If this is an over night or more days problem it may be a bad check valve in the fuel pump on the frame letting all the fuel drain back into the fuel tanks.
Letting a truck with this fuel system set is not good for the fuel selector valve and the "O" rings can stick and maybe cause low fuel pressure as the boost fuel pumps fuel may go into the other tank.
The other pressures you listed do not mean much as there is no reference at those operations.
A brief WOT should be about 40psi or grounding pin #6 of the self-test plug at KOEO would also be 40psi.
Does it start right back up after it has ran and then cooled a bit? If this is an over night or more days problem it may be a bad check valve in the fuel pump on the frame letting all the fuel drain back into the fuel tanks.
Letting a truck with this fuel system set is not good for the fuel selector valve and the "O" rings can stick and maybe cause low fuel pressure as the boost fuel pumps fuel may go into the other tank.
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I shoulda mentioned that. At first it was only after sitting over night. The longer it sat the harder it was. But then the other day it start being every time I tried to start it. But if I start it right back up its not to bad taking only a few seconds, then the longer it sits the worse it gets. Do you think throw a pump at the problem (the one on the frame rail) if I can find my receipt won't cost me anything but time anyway. Or could it be the tank selector valve? My original thought was the frame rail pump but when I saw the pressure jump with koeo I thought that was not the issue.
Thanks for the direction,
Z
Thanks for the direction,
Z
Lead Driver
Joined: Mar 2006
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From: IL
Will it start right back up once the truck is warmed up? Maybe it's not fuel related. I though my FP was going bad but then I realized after the truck sits for long periods of time, moister was getting into the Dist cap. I changed the cap out and all is well. I found this out by spraying the cap and wires down with WD40, let it sit about 30 minutes and after I was able to clear the cylinders of fuel, it started right up.
Laughing Gas
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Pressure spec is 35-40psi
unplug the vacuum line to the pressure regulator on the fuel rail, that will raise the pressure a bit if the pump is working correctly.
If the pressure doesn't raise your high pressure pump is on the way out.
unplug the vacuum line to the pressure regulator on the fuel rail, that will raise the pressure a bit if the pump is working correctly.
If the pressure doesn't raise your high pressure pump is on the way out.
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Fleet Owner
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From: Easton,Ks
35 is to high for idle. If you get 35psi at idle you have a vacuum problem.
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Ok. I remember something that I will check. When I was swapping ignition parts the dang mad cap I got was real tight and when I pressed it down it cracked slightly, it's slight but I will look at it first thing tomorrow. When the truck sits 24hrs koeo pressure is only 10 or so. Then jumps to 35-40 while cranking and then settles quickly to 30 at idle, with a bump to near 40 with throttle. Does this mean anything more than what I've already reported?
No trouble spraying a light coat of we 40 under the dist cap?
Thank you gents! Getting somewhere.
No trouble spraying a light coat of we 40 under the dist cap?
Thank you gents! Getting somewhere.
Lead Driver
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Check your pressure as you shut the engine down, or after pressuring the rail via the fuel pump test. A quick pressure drop after either would be indicative of a leaky injector or bad check valve in the return . 10 seems low for koeo, if there's a leaky injector that'd explain a lot...seems like you may be losing prime.
Automatic choke on startup would rule out ect sensor....
Automatic choke on startup would rule out ect sensor....
Fleet Owner
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From: Easton,Ks
Your fuel pressures sound good also.
Lead Driver
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i missed where you said it took several minutes to leakdown after shutoff....been a while since I read the first post.
so, fuel pressure is good, doesn't seem to be leaky injectors or check valves, and it runs good once it starts.
does it start easily once its warmed up and shut down, restarted?
again, does it go into "automatic choke" mode when it does fire up cold? if it doesn't go rich fuel and high idle on cold startup ("automagic choke) the ECT sensor is probably the culprit. if it starts fine after its warmed up, that'd also be indicative of a faulty ECT.
so, fuel pressure is good, doesn't seem to be leaky injectors or check valves, and it runs good once it starts.
does it start easily once its warmed up and shut down, restarted?
again, does it go into "automatic choke" mode when it does fire up cold? if it doesn't go rich fuel and high idle on cold startup ("automagic choke) the ECT sensor is probably the culprit. if it starts fine after its warmed up, that'd also be indicative of a faulty ECT.
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