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where the interia switch

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Old Jun 3, 2007 | 08:47 PM
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where the interia switch

Im having fuel pressure problems. Where can I find my inertia switch? I have an 88 f150 V8 5.0 XLT Lariet. Cant seem to find it. Thanks
 
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Old Jun 3, 2007 | 09:07 PM
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I have the same truck. It is inside on the firewall drivers side to the left and up. Use a flashlight and you will see it easier. Its got a recessed button on top. If it has tripped it wil be up.
 
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Old Jun 3, 2007 | 11:36 PM
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If the inertia switch is tripped, the fuel pump won't run at all. What do you mean by "fuel pressure problems"?
 
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Old Jun 4, 2007 | 12:08 AM
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i changed my injectors and now the pressure reads at 20 psi and then slowly falls.
 
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Old Jun 4, 2007 | 08:26 AM
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From: Easton,Ks
Originally Posted by specialist484
i changed my injectors and now the pressure reads at 20 psi and then slowly falls.
Sounds like a bad injector or fuel pressure regulator.

Why did you change the injectors?

Location of the inertia switch.
http://i54.photobucket.com/albums/g9...SwLocation.gif
 
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Old Jun 4, 2007 | 01:25 PM
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The mechanic told me i had bad injectors and I would need new ones. I kind of don't trust his opinion since he said that about my fuel pump and then my thermactor. Just keeps throwing parts out at me. I pulled the injectors out and they all fired and had a good spray. Put them back in and the pressure is lower. Im having it towed back to my house so I can pull the plenum and have a good look. Maybe I'll change the pressure regulator to be sure.
 
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Old Jun 4, 2007 | 03:11 PM
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From: Easton,Ks
Once you have pressure* and the engine is not running the only place it can leak off is the injectors and the Fuel pressure regulator.

*When you turn on the key the pump(s) will only run from one second with the engine not running or cranking. You may have to turn the key off and on a few times to bring the pressure all the way up to 41 PSI.
 
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Old Jun 4, 2007 | 03:14 PM
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specialist, If you are taking a fuel pressure reading at the rail and only getting 20 lbs and dropping it would indicate a bad pressure regulator. If im not mistaken injectors only fire when triggered. "Subford please jump in here." Replace the regulator first before tearing into it. Are you saying that when you pulled the injectors and checked the spray pattern it was a continued/uninterrupted spray?
 
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Old Jun 4, 2007 | 03:58 PM
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i put the injectors through a pretty crude cleaning. I took the filters, o-rings, and pintle caps off and soaked them in injector fluid overnight. The next day I sprayed carborator fluid through them while putting a 9 volt battery to them with alligator clips. Worked well to see the spray and if they fired off
 
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Old Jun 4, 2007 | 04:01 PM
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I actually think that he didn't seat one or more of the injectors, or even the FPR, on the rail and it's leaking fuel there.

A failed fuel pressure regulator would simply spike the pressure up to 60 psi and leave it there. Or if the diaphragm was ruptured, then I think the pressure would be ok as I've seen this diagnosed many times and I don't think one of the symptoms was ever that the truck wouldn't run or start.

It could also be a check valve in the pump - or is that only for the in-tank high pressure pump configuration?
 
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Old Jun 4, 2007 | 04:50 PM
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just put a new pump in. Is there a red neck way of checking the pressure at the pump or anywhere on the fuel line without having to buy a fuel pressure guage. I have an air pressure guage Ive been using at the rail.
I found it easier to put the rail in with the injectors rather than putting the injectors in, then fighting with the rail . Agree?
 
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Old Jun 4, 2007 | 04:59 PM
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From: Easton,Ks
Originally Posted by andym
I actually think that he didn't seat one or more of the injectors, or even the FPR, on the rail and it's leaking fuel there.

A failed fuel pressure regulator would simply spike the pressure up to 60 psi and leave it there. Or if the diaphragm was ruptured, then I think the pressure would be ok as I've seen this diagnosed many times and I don't think one of the symptoms was ever that the truck wouldn't run or start.

It could also be a check valve in the pump - or is that only for the in-tank high pressure pump configuration?
The check valve is in the Hi-Pressure pump on the frame below the driver’s door.

The in-tank pumps are just booster pumps and are only needed if you take the tank below 1/4 tank, go up a hill or run a tank dry. They are also used to shift the fuel selector valve to the running tanks pump.

If the diaphragm is busted in the fuel pressure regulator, the fuel pressure regulator let gas will come out of the nipple on top and go into #4 cylinder and fill it with gas. I do not know why it picks #4.


If he turns on the pumps with the vacuum hose off of the nipple of the regulator he would see gas coming out of the nipple it if the diaphragm is bad.

 

Last edited by subford; Jun 4, 2007 at 05:02 PM.
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Old Jun 4, 2007 | 06:29 PM
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If ya use a tire gauge to check your fuel pressure "You could be a redneck" Just a joke take no offense. I do wonder if you have a problem at all. Was the pressure tested by your mech with a fuel pressure gauge? Air is compressable. If there was just a tiny air bubble in your tire gauge you would no get a true reading. As far the pressure dropping I would not trust the air gauge to be accurate. When my fuel pressure regulator went bad it was at 100 LBS. (with a fuel pressure gauge) Which pump was replaced? The high pressure pump or the in tank pump? Also aside from what you have told us is the motor not running, starting or performing well?
 
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Old Jun 4, 2007 | 07:00 PM
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Its not running. It will turn over all day but wont start. The mechanic mentioned something about flooded cylinders and that he had to burn off the excess gas before he could get it to fire off a couple times, but still could not get it to start. It has spark at the plugs and fuel in the rail. I think I might try to pull the codes the red neck way and see if I can find anything worth mentioning. I have a hole in my EGR tube, would that stop it from starting?
 
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Old Jun 4, 2007 | 07:27 PM
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No, it wouldn't, but I don't think an air pressure gauge is a very accurate way to measure fuel pressure.
 
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