Dead fuel pump! Relay or MAF?

[davehaynes1]

Hi guys.
I am in the Australian outback and my car stopped running last week.
I hotwired my fuel pump and that got it running again but it's pretty lumpy on tick over.
First off i thought it must be the fuel pump relay but somebody has just suggested it could just as easily be the MAF.
Nobody has a fuel pump relay in this town. Only option I have is to order one from Melbourne (5000KM away) and $220.
I really don't want to order it only to realise it is the MAF broken.
Is there any way I can determine which one is broken?
Thanks guys!

 

[penbergm]

I do believe the the fuel pump bypass connector just bypasses the MAF. Round 2 plug connector right behind the MAF on my '86. With the key in the "ON" position and that connector jumpered, you should hear your fuel pump running.

 

[flyinhawaiian01]

turn key to on position, do not start. open maf to get to the flapper door. push door open slightly, you should hear a click, and hear the fuel pump running. If you do, door should be working correctly.

If it does not kick on, check harness at maf, clean contacts, check wires, test again.

If it is still not working, jump fuel relay then test again, if it works, relay is bad. I would not suggest running vehicle with jumped relay. I would suggest buying a standard relay (30A relay should work) for a couple bucks then wire that into the stock relay's port by using short jumpers and flat blade crimp connectors.

You did not mention what model you have, 5 speed or auto, 22re/3vze/2lt/etc.. There are a few other components depending on what you have. Here's a visual of all the parts for the fuel pump on most '80's/90's toyotas:

I'd check the switches that your vehicle may have too.

 

[Ahlem]

You can test the relay unplugged from the vehicle. If you have some sort of 12 volt power source (car battery) and a light bulb with leads and look carefully to see if you have the brand of relay with the diagram molded into the plastic housing. Energizing the relay should turn on the light bulb if you jumper it all in correctly. You can also feel the relay activate if you put your finger on it but should actually test the circuit to be sure the contacts are not fried inside. I don't know if the relay is the same as one of the others in the fuse box but might be and worth an interchange. On some older BMW models, you can swap relays around.

 

[davehaynes1]

Thanks for your replys!
Forgot to mention, I have a '93 3vze manual.

I can't test the MAF unless I put in a known good relay or jump it and I'm not too sure yet what pins should jump (at the momemt I have the fuel pump hot wired not jumped)
The relay I have is a 5 pin duel relay, Toyota have been telling me it's a special kind of relay, expensive and hard to find!

If somebody could tell me which two pins to jump that would be great as I could then find out if it's MAF or rule it out completely.

Thanks alot guys

 

[davehaynes1]

The other thing I'm wondering is if I do jump the relay that will bypass the MAF aswell won't it?
So the only way I can test if it's the MAF is to put a known working relay in??

 

[flyinhawaiian01]

Can you post a pic of that relay (or find the exact one online)? If we see it, maybe we can determine what wires go where.

As for a "special relay", I guess its possible, but a relay is nothing more than a remote switch, and being a double pole relay is not really anything special. You can get relays in several different forms, these are the most common ones:

I would be willing to bet its a double pole single throw relay, which you could make out of 2 standard relays for about 10 bucks, maybe less if you can find 'em there cheaper!

As for jumping the relay at the check connector, shorting pins FP and +B does exactly that, so if you're using the jump connector now, and it still does not work, you've basically removed the relay, the MAF and the clutch start switch inputs to the relay completely which says you have something else going on.

Check to see if you have +12VDC coming out at the check connector first, then jump the two pins, see if you hear the fuel pump running and/or if it will start. If it does, then go through and check each of the three items, MAF door, clutch start switch and power at the relay.

 

[jbtvt]

You have a VAFM on that engine, not a MAF. If the truck runs correctly with +B and FP jumpered it is most likely your circuit opening relay, passenger kickplate. These can be serviced, I made a video - https://www.youtube.com/watch?v=V8l9QvLAajA

If +B FP does nothing it might be the pump relay under the hood.

 

[davehaynes1]

That's another problem I have.
The relay under the hood is not there.....

 

[davehaynes1]

Right.....
So I've just put the relay back in as I was planning just lose the appature pin with my finger just to test relay or MAF and before I even touched it the truck started.
So the relay works... Guess I just have an intermittent problem with it.

 

[jbtvt]

That's another problem I have.
The relay under the hood is not there.....

Right.....
So I've just put the relay back in as I was planning just lose the appature pin with my finger just to test relay or MAF and before I even touched it the truck started.
So the relay works... Guess I just have an intermittent problem with it.

What relay are you testing then? EFI = electronic fuel injection... Once again, you do not have a MAF, completely different part

 

[davehaynes1]

The relay i have been testing was the one behind the glove box on the passenger side a pillar. (bare in mind i have a Right hand drive here in Australia)
The relay in the fuse box in the engine bay is missing, no relay, no plug for a relay and no wiring there. so i have no idea where that one could be!

Ive put the relay back in now and removed the hot wire to the fuel pump and the car starts every time now, somehow the relay seems to have fixed itself by being in a box for a couple days.... weird!!


The car starts and runs fine, but after cruising for a while when i come to a stop at traffic lights or at a junction the car idles very rough and will often stall itself...
Could this still be due to a faulty relay? as i understand the relay i was testing has two circuits, one to turn thepump on when the ignition is on to prime it, and a second circuit to run the pump once the engine is running.
Or could it run bad on idle due to a faulty VAFM?

Thanks!

 

[flyinhawaiian01]

how were the spade lugs on the relay? If they were corroded or black, I'd clean them up a bit with some sandpaper (like 600 grit, don't use 80!) and a little dielectric grease on them would probably be a good thing to do. Also check the other side's wiring for the relay, clean that up too, make sure they are tight on each of the spade lugs on the relay. If there are pit marks on the spade lugs on the relay, or black burn marks, check those wires to make sure the crimp is tight when its plugged in.

I'm unfamiliar with the VAFM, only the older MAFs, so try using the other poster's advice on that. I'd still check and clean any wiring connection to the VAFM, its free and doesn't take but a few minutes to do.

 

[davehaynes1]

all of the plugs and spades were clean. I just took the relay apart, cleaned with rubbing alcohol and applied some WD40 to drive out any moisture as there was some rust inside the relay. then i put it all back together and sealed up the outside to prevent any moisture getting in.

 

[flyinhawaiian01]

Could have been the contacts inside of the relay, its the same thing as a starter solenoid, basically. The contact plate may have had a carbon buildup and your alcohol may have cleaned it enough to get a better contact.

I wouldn't use wd40 in there though, when that thing arcs in there, it will burn the wd40 film and create another carbonized area. I'd just clean it really well with alcohol then stick it back in there with no oils of any sort. If its getting wet to the point of corrosion, you might wanna tape it around the body and base. That may stop a bit of that water getting in there--or stop fording oceans! :bounce:

 

[davehaynes1]

I've used some windscreen sealant on it. Should keep it pretty dry!

 

[jbtvt]

The water usually gets on your circuit opening relay through the bottom of the windshield, near ubiquitous problem. Dunno about RHDs but suspect they're the same. If you have water there you will also have water on the spade connectors at the relay backside which will rust and increase resistance and heat and eventually melt the wiring. You need to stop water getting behind your dash. Here's the fix -

I've fixed this issue on multiple vehicles without recurrence, for up to four years and counting at this point. First pull all the trim around the entire windshield, then scrape all loose rust using a screwdriver and run a rough sandpaper thoroughly over it. If you need to paint any areas make sure they're extra clean. Blow out the joint and treat with phosphoric acid per directions on bottle (or as a second choice, any phosphoric acid containing primer).

If you can't cover the entire affected area with caulking and need to paint, follow acid treatment with primer and paint. Let dry and then masking tape both sides of the joint all the way around the windshield and fill with Dow Corning 795 silicone sealant. This is not your typical hardware store caulk, it is professional glaziers sealant and makes all the difference - does not shrink or oxidize at all and has unsurpassed adhesion and flexibility. It's sold by industrial supply stores, or online at Amazon, not cheap, but worth it unless you want to do this every year. Finally, tool the joint with a plastic putty knife, and throw away that worthless, water-holding trim.

My windshield, before cleaning up the joints after it dries -

 

[chuck brixey]

Fuel pump relay.

I have a 94 4runner the only way the fuel pump will work is if I bypass the fuel pump relay. wont start.

 

[Brownfaux]

Chuck are you jumping the diagnostic terminal or wiring straight to the fuel pump?

I just sorted out the same problem and replacing the COR worked for me. Then I left out my EFI fuse on accident and had to troubleshoot it again. Are you trying to fix it or just just stating your solution to the OPs old problem?


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