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Replacing 1996 4.0L upper intake gaskets & injector seals


generic

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I need to replace the fuel-rail-to-lower-intake gasket(s) on my 1996 4.0L OHV as they have begun to get sucked into the front and rear pair of intake ports. Mine is the plastic spacer (~3/16" thick) sandwiched between 2 thinner gaskets (paper I think, don't have them off yet). I have the intake plenum removed (and thus all associated lines, connectors and throttle/cruise cables) as well as the coil pack and plug wires. Next up is removing the fuel rail and injectors and I want to be sure I do it right (I've already had a wonderful experience with gas in my eyes, nose and mouth while replacing the fuel filter, despite taking every precaution and following every step for depressurizing the system). I have a few days before I can move forward so it's a good time to dig into a few remaining questions:

1) As I can't crank the engine at this point, is there a better method for relieving fuel pressure than depressing the schrader valve and creating a mess/hazard?

2) Should I cap off the fuel supply & return lines after disconnecting them from the fuel rail? Or should I not even bother disconnecting them and try to move the fuel rail around with them connected? Note: I will probably have a fuel pressure gauge attached at the schrader valve the entire time so I can be sure there is no pressure in the system while working on it (yes, I am still gunshy after the fuel filter incident!).

3) This one is more from curiosity as I will leave it opened anyway... Does loosening or removing the gas cap help relieve pressure or just prevent it from building back up?

4) For lubing the new injector O-rings (Fel-Pro), some people say to use Vaseline or gear oil (do they mean like 90W differential lube?), yet others say to NOT use petroleum products at all, and still others say to not use petroleum products while recommending petroleum jelly :)icon_confused:), and then some say to use dilluted dish soap or cooking oil. LOL! The only consensus I've seen is to not use silicon-anything. I realise a forum is not always the best place to ask for an authoritative answer, but I don't want my new O-rings drying out or disintegrating. What is the safe recommendation for use with these O-rings?

5) The torque specs I've seen for the intake manifold studs were for the '97 4.0L and given as 9-11lb/ft. Can anyone confirm this for 1996 ('96-'98 seemed to each employ different intake gasket configurations)? Also, I marked each stud's position before wrenching and noticed that one of them began to turn when I loosened its plenum nut. After removing the nut, I set my torque wrench to 10lb/ft and tightened the stud but it clicked well before my mark was back in the original location. I haven't torqued it any further as several people have said they break easy? The plenum nuts are also spec'd at 15-18lb/ft for 1997, though Ford's TSB said 18.5lb/ft after installing the improved gasket, can anyone confirm this spec for the '96 as well?
 


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adsm08

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1) The cleanest way to relieve pressure if you can't crank the engine is to attach a gauge that has a pressure relief. All of my fuel pressure gauges have a clear, open ended hose, and a pressure release button. It is nice since you can stick the line in a drain pan or gas can or something. I think most pressure gauges have them now.

2) If you intend to remove the injectors to service the o-rings I would disconnect the lines and remove the rail completely. It will make the job much easier if you can move the rail around freely.

While I understand that you are gun shy with fuel pressure build up after presumably being sprayed when disconnecting a line without releasing the pressure first the fuel pump is the only thing that builds pressure in the fuel system. If nobody turns the key on after you relieve the system you won't have any fuel pressure to worry about.

3) Removing the fuel cap will do neither of those things. It will just let gas evaporate from your tank. As I said, running the fuel pump is the only way to build pressure in the fuel system.

4) I too have seen lots of different opinions on what is best to use for lubing the injector o-rings. The Ford shop manual says to use engine oil. Also, it doesn't prohibit the use of "silicone anything", but rather the use of silicone grease, like dielectric or caliper grease, not because it will damage the rubber, but because it can plug up the injector and since silicone is resistant to petroleum products and heat gas and heat won't melt it and clear the blockage. I usually use WD-40 myself.

5) The 96 book says the studs should be 7-10 ft-lb for the fuel rail, 15-18 for the manifold nuts, I know nothing about a revised spec for a revised gasket. Since I have not bothered to actually torque my own intake nuts, just use the calibrated arm technique and have had zero issues I can't believe that .5 ft lbs will really make that much of a difference.
 
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97RangerXLT

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When I did my gaskets in the above linked write up, I just put a shop towel around the shrader valve and stood to the side when depressing it with a small screwdriver. not much came out.

As for the injector o-rings, I used motor oil to make them easier to work with. I totally agree with ADSM on having the fuel rail out, and having the entire lower intake in my lap while putting the injectors back in made it even more easy. but that is a decision to make: do you want to deal with the lower intake gasket as well.

AJ
 

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Thanks guys! Just waiting on my gaskets to arrive and then I should be in business. I am not doing the lower intake gasket yet as I don't have any reason to suspect a leak there.

The fuel pressure tester I rented last time was great, had the relief valve and clear tube (which also showed me just how nasty the gas was coming through the old filter lol). But I still relieved the initial pressure by killing the pump relay and cranking the engine because I wasn't sure if attaching the gauge to the schrader valve while still pressurized wouldn't cause it to spray/leak (it was an Actron kit and a couple of people had remarked about the poor QC on their Ford adapter adapter). Anyway, I'm good with relieving it at the schrader as you suggested.

Oh, do I need to cap/plug the fuel lines after I disconnect them from the rail? Tank is near empty right now (gauge light just came on just before I shut her off last time). When I tested the fuel pressure recently, if I let it sit for a few minutes and then hit the relief valve, I would still get some very small amount of fuel draining out into the clear tube (maybe just ambient temperature causing the fuel vapor to expand?). If I should cap them, is there any special kind of cap or can I just rig up something?
 

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I didn't bother capping mine. I just moved them to the side to get them out of the way. If you are going to leave them off for a while and are worried about dirt or bugs or moisture getting in take a few sandwich bags and some rubber bands to seal them

Sent from my SM-N910V using Tapatalk
 

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Awesome, thank you!
 

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Yeah, I'm with AJ on capping them. I don't bother unless I am going to have the lines open for more than two weeks.
 

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Just an update to say there was no issue at all re fuel pressure, only got a little dribble while attaching the gauge. Truck sitting for a day or two was plenty to fully depressurize the system. The fuel rail, however, was still full of fuel, lol. Only a couple drops came out when I disconnected the lines, the rest came out when the #6 injector popped out of the rail. Had to make a mad dash for some rags to sop it all up! In hindsight, it might have been wise to leave the return line connected and tilt the rail to drain it into the return line. No harm, no foul though, just had to put up with the fumes while pulling the rail out.

I'm now working on cleaning the injector seats and then I should be able to button it all back up soon. This is the first time I've done this level of engine work on my own so I am definitely taking it slow and steady. Thanks again, guys, for all your help!
 


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