Fuel pump bad?
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Junior User
Joined: Apr 2008
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Fuel pump bad?
I ahve a 1999 7.3 and is having some trouble starting in the cold in the morning. Glow plugs and relay should all be good relaced 6 months ago. when it starts it is firing on all cylinders but will come up to idle speed or close to it then slowly drop and die, pedal to the floor or not. after a try or two it will either idle and romp up and down a bit till it stops or just idle fine. just replaced the fuel filter and didnt look to dirty for 6 or 8 thousand miles. did a test a mechanic had me try pulled the fuel bowl cap off and pushing down on the filter it took 10-12 seconds to fill the bowl with the ignition on, should have taken less than 5 i guess. the fuel pump is buzzing but not all that loud hard to hear if your not on the ground. my question is the pump bad or are the screens in the tank dirty dont want to buy a $200 pump and have that not be a problem. I have a full tank and not to interested in dropping it either. Wont be out of fuel for a month maybe, i live close to work and work six days a week and cant go anywhere at the moment to burn it.
Cargo Master
Joined: May 2010
Posts: 3,047
Likes: 9
From: Snohomish, WA
You would be better off to put a gauge in one of the fuel bowl ports and check pressure. You could have a fuel problem, but if you have good fuel pressure you will know it is something else.
One thing that can often cause issues like that is a faulty ICP sensor, You can disconnect the plug on the ICP and check for oil in the contacts. If it is dry leave the plug off and try to start it. If it starts normally, then the ICP is the culprit.
Either way you do it, don't throw parts at it, a little troubleshooting should provide you with the correct path.
One thing that can often cause issues like that is a faulty ICP sensor, You can disconnect the plug on the ICP and check for oil in the contacts. If it is dry leave the plug off and try to start it. If it starts normally, then the ICP is the culprit.
Either way you do it, don't throw parts at it, a little troubleshooting should provide you with the correct path.
Cargo Master
Joined: May 2010
Posts: 3,047
Likes: 9
From: Snohomish, WA
Did you unplug it and it starts fine? If so an ICP sensor is only about $100. Still not cheap, but better than a fuel pump.
You can leave it unplugged, not the best thing to do, but in a pinch I suppose. The PCM will treat it as a out of range, you should have a CEL too.
Not always, sometimes if it is hunting the pressure signal will bounce and that causes the romping you mention.
You can leave it unplugged, not the best thing to do, but in a pinch I suppose. The PCM will treat it as a out of range, you should have a CEL too.
But a faulty ICP sensor usually spits out codes when it starts to go out doesn't it.
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So it was another day of poor starting today, i started my truck up just like usual and it started to romp back and forth so i shut it down. pulled the icp sensor plug and started it again it fired about the same didnt romp at all just idled wierd camp up to almost 1000rmp right off the bat and stayed until i shut it down again and plugged the icp back in and started it a third time and it was fine no romping. I am starting to lean in the direction of the icp not wanting to work right away when its cold, but i still dont understand the extremly poor fuel economy. I think i may still have more than one problem becouse the truck is under fueled all threw the power ban. It has an 80hp eco tune on it and used to smoke a lot if you got on it, now only a small puff when boost hits. dont know if the icp would also do that or not.
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Cargo Master
Joined: May 2010
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From: Snohomish, WA
That can point to faulty ICP too. Having ICP that is incorrect will effect power, smoke, and throttle response.
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Senior User
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From: Issaquah, WA
You can drive it with the ICP unlpugged indefinitely and get 90% same performance as stock. I know, I drove that way for a month. You need to get a fuel pressure reading to rule out clogged screens.
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Junior User
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Thanks guys will give it a drive with it unplugged around town a bit and to my parents for thanks giving 150 miles highway and let you know what happens. plan on dropping the tank to do the hutch mods tomorow anyway becouse i want to know what is making my fuel guage bounce around so bad. with those two areas investigated should be a little easier to find the problem if that isnt one of them.
