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I have a fuel leak from the EFI system, (I think) because a small screw and o-ring fell out of a part I can't identify. Can anyone tell me what this part is/does; if I just need to replace the old o-ring; or if I need to replace a part, or assembly. Also, would such a leak explain why my engine is missing under load?
I believe, and I may well be wrong, but I believe that's the Pulsation Damper. Used to even out fuel pressure pulses from the fuel pump.
Note red arrow.
If you can smell fuel, REPLACE IT. You don't want to be driving along and see fire under the hood!
Yes, it could be the cause of your engine trouble. It may not be allowing sufficient fuel into the fuel rail to feed the injectors. I'm not exactly sure what the screw that fell out does, but you should never need to adjust it for any reason I can think of. I never have on my 87 4Runner.
Always remember, never, ever, reuse the crush washers anywhere in the fuel system. There's one on the Pulsation Damper, where it screws into the fuel rail. If the new one comes with one, great. If not, you'll have to buy one from someplace. Dealer is the best choice. Not all the crush washers are the same size, so make sure you get the one you need. They aren't expensive, and are vital to preventing leakage from the fuel system, which is deadly dangerous. Fuel leaks scare me spitless.
Make sure you mark the package they come in as to where they are used, in case you don't need the extras. Eventually, you can wind up with a nice collection of crush washers, and you want to be sure to use them in the right places.
Always get a couple extra crush washers than you think you'll need. If you only have one, the malicious little bugger WILL jump out of your hand, fall down under the truck, and vanish. They are truly malicious that way.
Also, pay attention to the torque value the FSM recommends. You can snug things a little tighter if there's still seepage from the crush washer, but don't just crank down on it. Just a little snugging down is the way to go.
You'll probably need to pull the throttle body to get to the pulsation damper, so you'll need a new gasket for that, too. Unless a gasket, like for the throttle body, is brand new, just installed, you'll definitely need a new one. Think about how long it's been in there. You'll NEED a new one. You will probably need to do some scraping to get the old one off. Use something plastic to scrape with. You don't want to damage the mating faces the gasket seals onto, or you can get an air leak, and that will cause real troubles.
I believe, and I may well be wrong, but I believe that's the Pulsation Damper. Used to even out fuel pressure pulses from the fuel pump.
Note red arrow.
If you can smell fuel, REPLACE IT. You don't want to be driving along and see fire under the hood!
Yes, it could be the cause of your engine trouble. It may not be allowing sufficient fuel into the fuel rail to feed the injectors. I'm not exactly sure what the screw that fell out does, but you should never need to adjust it for any reason I can think of. I never have on my 87 4Runner.
Always remember, never, ever, reuse the crush washers anywhere in the fuel system. There's one on the Pulsation Damper, where it screws into the fuel rail. If the new one comes with one, great. If not, you'll have to buy one from someplace. Dealer is the best choice. Not all the crush washers are the same size, so make sure you get the one you need. They aren't expensive, and are vital to preventing leakage from the fuel system, which is deadly dangerous. Fuel leaks scare me spitless.
Make sure you mark the package they come in as to where they are used, in case you don't need the extras. Eventually, you can wind up with a nice collection of crush washers, and you want to be sure to use them in the right places.
Always get a couple extra crush washers than you think you'll need. If you only have one, the malicious little bugger WILL jump out of your hand, fall down under the truck, and vanish. They are truly malicious that way.
Also, pay attention to the torque value the FSM recommends. You can snug things a little tighter if there's still seepage from the crush washer, but don't just crank down on it. Just a little snugging down is the way to go.
You'll probably need to pull the throttle body to get to the pulsation damper, so you'll need a new gasket for that, too. Unless a gasket, like for the throttle body, is brand new, just installed, you'll definitely need a new one. Think about how long it's been in there. You'll NEED a new one. You will probably need to do some scraping to get the old one off. Use something plastic to scrape with. You don't want to damage the mating faces the gasket seals onto, or you can get an air leak, and that will cause real troubles.
Good luck to ya!
Pat☺
Thanks, Pat, for your excellent advice! I now feel like I can fix this. I'm hoping not to have to pull the throttle body to replace the damper.
I can't recall off the top of my head whether you HAVE to or not. I think you do, but I am often mistaken. You really just need enough room to get a wrench in there, and apply enough torque to get it loose to start. Once it breaks loose, it just unscrews with your fingers. Not tight threads at all. Remember, though, it takes 2 wrenches to break it loose. There's the nut ON the fuel rail that the damper screws into, and the nut on the damper, that you have to turn. Same for torquing it back down. you'll have to fit 2 wrenches in there. The fixed one, on the fuel rail, has a tab that sticks down, to hold it in place. Makes identifying which is which easier. The wrench for the damper itself goes right below that tab. When I did mine, I had taken off both the throttle body and the intake manifold, so I could get to it easily. I put the two wrenches on, with their shafts offset by one place, one flat of the nuts, and was able to just grab them with one hand and squeeeeeeeze. I've got big hands, though...
Putting it back on, just remember to torque it correctly. Too tight, and the crush washers leak. Too loose, and they leak too, though. I'll see if I can dig up the torque specs for the pulsation damper. It's not real high. I think about 25 ft/lbs, but don't take that as gospel. Don't rely on it, IOW. Find the RIGHT torque spec.
Having said that, if you have to remove the TB, it's not really all that hard. When you pull the bolts out, put them into a piece of cardboard in the positions that they were in on the TB. That way, you know for sure, when you put them back in, the right length, thread pitch, etc, is in the right place. Their torque specs are in the FSM, under the Engine Mechanical repair section. Right up front.
Also, If you DO have to pull the TB off, buy a new gasket for it BEFORE you start. Who knows HOW long it's been on there. You'll probably wind up having to scrape parts of it off of one side or the other. Or both. Use a plastic scraper, or brush, so you don't scrape up the aluminum everything is made of.
Thanks, Pat, I'll check the torque spec when I replace the pulsation damper. I only needed to use one wrench to get the old one off...a decent quality crescent wrench, which was strong and short enough to work perfectly. I thought two wrenches were required only if there was a risk of bending/breaking fuel line above the damper.
I'll have to buy a couple new crush washers. Also, I don't think a new plastic cover for the damper will be included. Is it important to replace the old plastic cover with a new one? What is its function? The old one is brittle, with some small cracks...but if it's just a dust cover, can I use the old one?
I may be wrong, as usual, but I believe that the plastic cover is a dust/dirt cover. Keeps the icky out. If you can get it to go back on, I would just reuse the old one.
I'm a cheap...errrr...FRUGAL....yeah very frugal...SOB, though.
BTW: Found the torque spec for the pulsation damper.
Good luck! I'm glad you could get in there and remove the PD with just one wrench. It's been nearly 20 years since I had mine off, so my memory isn't the best thing to rely on. Also, I did mine with the TB off, since I was replacing the head gasket after a "friend" cracked the head by overheating the truck, several times, trying to get it back to me after he threw the water pump belt. Could have replaced the belt with the old one I kept in the back, and the tools I keep in it, but noooooo...
Anywho...
Apr 11, 2021 | 09:56 AM
Use a plastic scraper, or brush, so you don't scrape up the aluminum everything is made of.
