Tony H.

I did the test on the fuel pump to see if I hear it in the back of the car after letting the battery be unpluged for days, I hooked back up the charged battery and I had the key in the on position when I kooked the battery up so I could be at the rear of the car to listen for the fuel pump, I did not hear anything like a fuel pump staring up in fact I heard nothing at all unless the pump is very very quite.

I am not sure where the pump is actually located in the car but I will try to wait and hear back on this thread as to how I can find it first then make sure it is not just very very quite when it is first engaged. I realy did not hear any noise in the rear of the car and I had my head down inside the car by the battery box and heard nothing like a pump sound. Any ideas on where to go from here.

I still do not have a pressure guage for the rail to check pressure but not hearing the pump is suspect at best for now. I am wondering if maybe the relay for the pump is bad as well or maybe that is all that is bad and not allowing the power to the pump, I am not an electrician but I do know how to find the relay I have the chart for them. It is the 4th one from the right top row in my car. (XX) in the chart. But what would tell if it is bad or not, I will pull it and look for burnt areas or loose relay connection but after that I would not know if internally it is bad without just changing it out with a known good one or swapping it with some other one in the panel that is the same type.

Any ideas on how I should proceed is wanted and needed but most of all I am hoping and thankful.

Thanks Tony H.

Tony H.

I wanted to also ask it looks like the relay is a very common relay in the chart, can I swap it with the starter relay which I know works to see if the will make the pump make noise, they are the same number relay on the chart along with others as well? Or will that do damge to the car or the panel itself?
Thanks

jayc67

Yes, you can use the horn relay as well. That's a good one to use. You are right, that relay is most common. I believe there are 9 of them used in the car, can't remember for sure but there are plenty. And no it won't hurt a thing to swap relays out as long as you use the same type.

Your fuel pump is on the right side behind the rear bumper fascia. There's a little cover under there that covers the fuel pump and filter right at the tank exit. I believe there's only one pump on the 86.

Did you do the jumper test so the pump will run all the time? That's the best way to try to listen for it. This also removes the relay from the picture, helping isolate the problem.

http://members.rennlist.com/v1uhoh/jumping.htm

GlenL

The "53" relays are common. Check for something else that uses it, like maybe the horn or defroster, and swap with that. Then you'll be able to start the car.

The fuel pump is under a panel on the rear of the tank, roughly below the right-side back-up light.

davek9

+ one what the others have said, but make sure your horn works before using the horn relay

jcorenman

Tony,

I assume this is a continuation of your "still not running smooth" thread?
https://rennlist.com/forums/928-foru...ng-smooth.html

WallyP's post#27 was a really good summary of what needs checking:
https://rennlist.com/forums/7167449-post27.html

The fuel pump is at the back of the car under a metal cover attached to the fuel tank (on the right side, visible from under the bumper cover).

I do not believe that the fuel pump will run until the engine is cranked however- it is controlled by relay XX (and fuse 42) on an '86 but needs a signal from the LH to start pumping fuel.

The best way to eliminate fuel-pump problems is to fit a fuel-pressure gauge to the front of the right-side fuel rail (the car's right side that is), see the pic in your previous thread. Roger at 928's-R-us can supply this as a kit with the proper fitting and gauge (ROG100 here, email roger (at) 928sRUs (dot) com, web site www.928srus.com).

Some folks don't like to leave a gauge in place (another possible fuel leak), that's fine but having it in place while trying to troubleshoot problems is invaluable. Don't try to cobble something together, it is a goofy metric ball-end fitting that is very hard to find. Just get the kit from Roger.

To check the fuel pump you need to remove relay XX and jumper it, see post #42 in this recent thread:
https://rennlist.com/forums/928-foru...l-light-3.html

Then turn the key on, walk around to the back of the car and listen-- you should hear a quiet humming or buzzing fom behind the right-side bumper. If you hear that, you should have fuel pressure.

Cheers, Jim

SteveG

Tony: It sounds like the pump relay is bad; the "253" is the most common, you should order a couple spares. People usu swap with the horn (XII) as you can check it immediately before pulling, toot = good relay. However they are a bitch to get out and I have destroyed more than one doing it. So a jumper as pictured in the other thread is a good option, i.e., you only remove XX. Either way the XX has to come out. Disconnect the batt before jamming around in the panel. Try the twist, jiggle-in-all-directions-and-twist-some-more method. If you have really strong fingers, that will work. Or maybe not. There are theads here with suggestions for small pry tools to use. If you get some space under the relay you might get a long zip tie slipped between panel and the relay. Then pull and twist. Pliers and other tools designed esp for grasping the relay work (?) or separate the cube from the prongs stuck in the panel. YMMV.

A better option and an item many carry with them is a single pole on/off switch at the end of about 3 feet of lamp cord, the spade ends at the other end. That way you can turn the "jump" on/off from the driver's seat.

So the procedure would be: disconnect batt. Get the relay out. Insert jumper. Connect battery. You should hear the pump. Run to seat, key to start position. If it starts, you have your answer. If it doesn't start, you at least know it isn't the relay. Don't run the pump for more than a few seconds w/o the engine running as you can burn out the pump. HTH. Just remember this is all part of the bonding process.

jayc67

Why would that burn the pump up? The unused fuel just circulates back to the tank, as long as it's actually pumping.

Tony H.

OK I will do the aformentioned items to check to pump I will jumper the relay to see if I hear the pump running always and I will also switch relays with other I know work my horn is working fine I'll use that one.

In my last thread someone had mention that the engine did not need to be cranked to hear the pump startup, I read a thread about not starting earlier and the stated the groung strap was causing issues by the battery, My car cranks and fires but does not run and if it does run, runs like crap.

Ther are some more areas I need to look at but wanted to ckeck electrical items and fuel pump, also a few ground points I may need to verify and clean and the strap point at the battery ground does not look good rusty looking, but I have never had the car not try to start due to lack of ignition, it always turns over and tries to start so I am guessing the fuel is getting there, My plugs smelled of fuel when I removed them, I am going to do the test anyway to make sure I hear the pump run when jumped, does the car have to be turned over to make the pump run or not jumping it tells me me suspect bad relay, but if it has to be cranked then I will not know for sure it is bad but will know the pump is running only. I hope to have a helper turn the car over so I can check for spark at the plugs while cranking and also check to make sure I hear the injectors clicking but presently I have no help which makes it almost impossible to do it all, without help.

I must be the only person in North Florida with a 928????

Let me now if the cranking is nessasary or not and I will let everyone know what I have found. I will call Roger the check on price for a kit for the pressure guage more cash to spend.

This really came on all at once while running at a light it started to miss and sputter like unheard of missing. My connection at the ground strap on battery is like welded in place it has been on so long the bolt seems like it may break off if I try to turn the wing nut, but I will try anyway. under the car ground has yet to be check near left side engine. 14 pin and other ground points have been cleaned and replaced including both points on the battery cables not just looked at cleaned.

Thanks Tony H.

jayc67

If the relay is in place the relay will only send power to the fuel pump if the engine is turning, in a nutshell. I believe it's the tach input that' controls that.

So, if you don't crank it the fuel pump won't run. That's what the jumper technique is for, to bypass all that and make the fuel pump run continuously.

SteveG

Jammed?

jayc67

Oh sure, sorry. Thought you meant just running it. Yes, if it's not running a couple of things can happen. 1) The pump can be damaged
2) The jumper wire can get hot enough to melt plastic in the electrical panel from the high current going through it, if the wire wasn't big enough (recent paperclip thread lol)

Bad bidness

Tony H.

Ok, Here is the result of the jumper of the relay to the pump when jumpered it runs continually, I am not sure what that tells me but that is what happened.

I did not turn the key on to see if it will start due to have ing many parts off the cat presently like the air box and filter, some of the intake is apart like the box are off of it to get at the plugs. can someone just tell me what the result of jumping the pump should have made me aware of other than the pump is working when powered. I know it tiold the fuse at 42 is good and the pump is running when supplied with power, but other than that I do not know what else it may be saying to me.
Thanks

jayc67

That's it. You can assume, with pretty fair certainty, that you have fuel pressure. So, when digging deeper into your problem I would leave the jumper in place and move on to the next steps. Disconnect it while you're not actually working on the car of course.....

It's just one small bit of information, but it's one of the easiest to remove from the "WTH is wrong" list.

But yes, that's all it told you. It's one of the most common problems, and easy to check, so it's usually the best place to start.

Now it could be something like fuel pressure regulator, you still may have a fuel starvation problem, but at least you have eliminated one thing for sure.

Tony H.

Quicky, when trying to see if I have spark at the plug should I have the fuel relay out so it does not pump fuel, and also should I have all of the plugs out or one at a time?

I am making sure of ground points, only one being an issue to check is the rear ground strap at the body, it's been on since day one I think I sure would hate to break it off..