Fuel Relay/Fuel Pump

[durangodoug]

My dad is letting me drive his Bronco for the summer, to get to work and all. I've been driving it with no problem at all until the other day. I pulled into the driveway and turned the engine off, like normal. The next day, the engine wouldn't turn over. I can hear the starter and it sounds like fuel isn't getting into the engine. I decided to check the boards around here and see what you guys had to say. I'm hearing that there may be a problem between the 2 fuel pumps or the relay. I'm thinking that it may be my relay since the problem was so sudden. The truck is a 95 Ford Bronco, V8, 5.0L engine I think, 171K miles. I've tried to find the fuel relay but I don't see it. I know you guys have said its next to the airbox and that its green, but all I see is a skinny gray relay and a huge, square shaped black relay. Any suggestions, you guys seem to know a lot about this stuff.

 

[Roadkill]

There is a box located rearward of the aircleaner box. Remove the cover and inside that box you will find fuses and relays. Here is a diagram for a '96. I'm not 100% certain that the '95 is identical but I think it is. Anyhow, there should be a diagram inside the box so this will at least give you an idea what you are looking for.



On this one, the fuel pump relay is number 2 and the fuse is number 16.

 

[durangodoug]

Thanks a lot for that diagram. I found what I needed. But I can't get out to get a new relay until tomorrow. I think I read earlier about cleaning the connection to the front fuel pump. Do you think its worth a try? Any other little, cheap things I can troubleshoot before I go out buying fuel pumps?

Thanks

 

[Roadkill]

Your '95 does not have a front fuel pump. It has only one, located inside the tank. You definately want to rule out other problems before spending $200 for a new pump and dropping the tank to install it. If you do not hear the pump running, make sure that power is getting to the pump. Check fuses, relays, inspect wiring and connectors for corrosion/dirt and good snug fit. Also don't forget to check the collision cutoff switch.

 

[bobstrat]

if you can hear the pump when you turn the key, im pretty sure that rules out the relay. i might check my ignition module if the fuel pump and relay all pass. mine went suddenly and without warning. and when they go she will not fire. timing light on the coil to distributor wire will show if shes hot or not. if not you'll have to check the coil and module.

maybe tell us a little more about whats going on when you try to start her. any noises, stuff like that.

 

[miesk5]

yo!

Does the Check Engine Light come on?

Yes, ck relay socket and do a wire/connector wiggle test.

If you can not hear the fp run when turning ket to start engine; then try swapping horn relay in there.

 

[durangodoug]

Ok guys, seems I was giving you some bad info. My dad killed the battery the other day trying to start the truck 100 times. I jumped it today and tried to start it. I can hear clicks coming from the relay and the truck did kinda start. The engine did turn over but for only about a second and then it quit. I called the repairman down the street and he is saying it may be the starter. And yes, the check engine light is coming on. Didn't think the Bronco could be so confusing, but thanks for all the help so far.

 

[bobstrat]

did you check for spark? im not getting how its the starter, if you were able to use it enough to **** the battery.

also when you turn the key to the run position (but not start) can you hear the fuel pump from under the truck as well as the couple clicks from the relays? if you only hear the clicks but no fuel pump then you may have a pump problem.

so there's two checks for you.

1. verify you can hear the pump for a second or two when the key is turned on. (but not start) if yes then,

2. check for spark from the distributor.

 

[footmaster]

i had a similar problem once....i drove to the gas station shut her off filled her up then it just wouldnt start....it was turnin just not gettin fuel......long story short i ended up cutting a hole in the back right above the tank and sendin a wire from the fuse box through my truck to the pump.......now when my key is in the forward position without starting it the pump runs all the time, no biggie.

 

[durangodoug]

Well I still don't hear the buzzing from the fuel pump, so I'm putting my money on that. My dad and the repairman still think its a starter issue. We're taking it in later on this week because I don't have the know-how to do any of this myself. Thanks for the tips and suggestions guys.

 

[bobstrat]

the only thing the starter does is spin the motor. if the truck turns over you don't have a starter problem. if you can't hear the fuel pump when the key is in the run position there's your problem.( it should hum for a second or two when you turn the key) i guess if youre not comfortable doing the repair, i'd take it somewhere too. it's really not that difficult to change the fuel pump. i recently did mine as well as the fuel tank, so if you have any questions i'd be happy to help you out. actually im getting ahead of myself. i'd verify voltage at the fuel pump connector first. the pump could be good but not getting power.

 

[bobstrat]

also, did you ever try miesk5's advice about swapping the horn relay into your fuel pump relay spot?

 

[viperfangs2]

Im betting its the fuel pump when my fuel pump went bad on my bronco 2 it just happed over night plus u said that it started for a few seconds and died that would be a sign of a bad fuel pump also were you really low on gas when ur dad tried to start the car 100 times cuz that will burn you fuel pump up!!! i have replace 3 fuel pumps 2 i had to drop the tank not fun but the fuel pump on my olds had a trunk assess panel which made my day trust me!!!!! Go luck [-o<

 

[durangodoug]

Ok guys, I'm 100% sure that its the fuel pump, going off of my research and all your knowledge. But would you guys mind telling me some symptoms the bronco would have if it was a starter issue? I would hate to tell my dad that the fuel pump is the problem and have the truck not start after the pump is replaced. Oh, and later on today I will try switching the fuel relay with the horn relay, what will that explain to me though?

Thanks again

 

[AQNW]

Doug, swapping the relay might tell you whether the relay itself is bad, and therefore not providing power to the fuel pump. I totally understand trying to keep costs down and not replacing parts unless necessary. I went thru this with a 97 Dodge Caravan, so let me try to explain what I learned.

Relays are used to switch power on a high amperage 12V circuit using a low amperage 12V circuit (This page explains relays in more detail: http://www.teamrocs.com/technical/pages/relay_basics.htm). So when you hit the horn, it sends a low amp signal to the relay which turns on the high amp horn circuit. Same for the fuel pump when you turn the key, the relay senses the ignition (low amp) is on and switches the high amp fuel pump circuit on. In my experience, if you don't hear the fuel pump spin up for a few seconds, it could be one of the following:

relay, fuel pump, fuel pump wiring, fuel pump ground, auto cutoff from PCM

Borrow or buy a cheapo multimeter that measures DC voltages and resistance (ohms) and confirm that you have 12V to pin30 of the fuel pump relay socket. If you don't have 12V to the relay, the cause is something before the relay (fuse, wiring, computer, etc.) and nothing after the relay will work.

If you have 12V at the relay, use a 6" piece of insulated wire stripped on both ends to jump between pin30 and pin87 (not 87A) in the relay socket. Be careful, as it could give you quite a shock. Jumping these pins with the key on should cause the fuel pump to spin a few seconds until it reaches pressure and automatically shuts off. Confirm that you hear the pump spin. If the pump spins, it proves that the wiring from the relay to the pump to ground is good. But it doesn't prove whether the pump is pushing appropriate fuel pressure.

If the pump doesn't spin, your work begins. Drain & drop the tank if necessary to remove the fuel pump assembly. With the pump out, you should be able to connect a car battery to the pumps positive and negative leads and cause the pump to spin. It'll have some fuel in it, and could shoot it fair distance, so connect the +/- wires to the pump first, then touch the +/- to the battery some distance away. I don't want to blow you, your dad and the garage to mars. If the pump doesn't spin, it's dead.

This overall technique can be used to diagnose any number of relay, wiring & circuit problems. After buying a new relay & used fuel pump on http://www.car-part.com, the problem with my Caravan turned out to be a bad computer. I bought a used computer from the aforementioned site, swapped it in and the 'Van started right up.

Good luck, Eric