9v at fuel pump, not 12... no start

the great him

the great him

Elite Member
so my no start is back...

i have 9.xx v at the pump plug under the rear seat, not 12 like it should. the circuit opening relay is brand new, along with the EFI and tail like relay(swapped tail like relay and COR just to make sure its not the relay[same relays]), and this did not make any difference. truck drove fine on my way to work. when i stopped for coffee it would not start again. it momentarily acted like it wanted to start but died abruptly before fully firing up, and that was that. cracked the fuel line under the hood and no fuel flow, then checked the tank pug under the rear seat and am getting only 9v when the key is turned... (its cranking hard and battery has standing 12.7v)

i did not have time to trace this any further back, as it was pouring rain out and i was already late for work, my secondary ride showed up to get me and thats as far as i got. does anyone have some suggestions on why i keep getting this. since swapping the stock fuel pump back in my labored starting has returned, or at least it was much more apparent this morning. not sure if it is because of the wet weather or not. not sure if this is a ground issue...

i came back after work for about 5 min to see if it would start, and still nothing... i wasnt gonna make my buddy wait all evening for me to fiddle with things so again thats where it stayed.

i did drive through a rather large puddle that was across the road just as i was turning into my stop for coffee. im not sure if this has anything to do with it or not
 
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the great him said:
so my no start is back...

i have 9.xx v at the pump plug under the rear seat, not 12 like it should. the circuit opening relay is brand new, along with the EFI and tail like relay(swapped tail like relay and COR just to make sure its not the relay[same relays]), and this did not make any difference. truck drove fine on my way to work. when i stopped for coffee it would not start again. it momentarily acted like it wanted to start but died abruptly before fully firing up, and that was that. cracked the fuel line under the hood and no fuel flow, then checked the tank pug under the rear seat and am getting only 9v when the key is turned... (its cranking hard and battery has standing 12.7v)

i did not have time to trace this any further back, as it was pouring rain out and i was already late for work, my secondary ride showed up to get me and thats as far as i got. does anyone have some suggestions on why i keep getting this. since swapping the stock fuel pump back in my labored starting has returned, or at least it was much more apparent this morning. not sure if it is because of the wet weather or not. not sure if this is a ground issue...

i came back after work for about 5 min to see if it would start, and still nothing... i wasnt gonna make my buddy wait all evening for me to fiddle with things so again thats where it stayed.

i did drive through a rather large puddle that was across the road just as i was turning into my stop for coffee. im not sure if this has anything to do with it or not
Click to expand...

OK you really need to go back to basics. Always check the easy things first, and record your findings so you don't have to recheck things.

The first thing I would check is the voltages AT the Circuit Opening Relay. Pull the relay and check terminal 5 of the connector. If you have 12V, jumper T5 to T3 and recheck at the pump, if still low the problem is between the relay and the pump, if not it's the relay or connection. If T5 is not 12V, check the next easy thing.

That would be the EFI relay. With the Relay pulled, again check T5 if 12V jumper to T3 and go back to T5 of the CO relay, if still good, bad relay or connector, if not 12V the problem is between the relays. If T5 is not 12V,
Check the next easy thing.

That is the 20A EFI fuse...

:popcorn:
 
IBallEngineer said:
OK you really need to go back to basics. Always check the easy things first, and record your findings so you don't have to recheck things.

The first thing I would check is the voltages AT the Circuit Opening Relay. Pull the relay and check terminal 5 of the connector. If you have 12V, jumper T5 to T3 and recheck at the pump, if still low the problem is between the relay and the pump, if not it's the relay or connection. If T5 is not 12V, check the next easy thing.

That would be the EFI relay. With the Relay pulled, again check T5 if 12V jumper to T3 and go back to T5 of the CO relay, if still good, bad relay or connector, if not 12V the problem is between the relays. If T5 is not 12V,
Check the next easy thing.

That is the 20A EFI fuse...

:popcorn:
Click to expand...

efi fuese is only 15 i though? at least thats whats in my truck. and there is no T5 on the relays... they are all 4 terminal relays...

thank you though. my trouble shooting skillz on electrical are about as much as a hippos
 
the great him said:
efi fuese is only 15 i though? at least thats whats in my truck. and there is no T5 on the relays... they are all 4 terminal relays...

thank you though. my trouble shooting skillz on electrical are about as much as a hippos
Click to expand...

The connector is labeled 1,2,3,5. Only 4 terminals, but there is no #4. With the key on, both relays will have 2 power sources, one for the load and one for the trigger. On the EFI relay 1 is power on the trigger side, and 5 is power on the load side. Here is the pin out for that relay, page 21.

http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/relayloc/relayloc.pdf

Here is the pin out for the CO relay, C6 on page 237

http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/connecto/connecto.pdf

Its not rocket science, you can do it!

:director:
 
Both the ground on the plug and the bolt to the seatbelts...

So checking further that voltage drop is acceptable under load of the starter... I hooked my truck to my friends Cummins and then tried again, voltage drop was not as bad, only dropped to 11v but still no fuel. Its begging to look more and more like the pump itself is the fualt. The last couple of days the starting was very long...
 
the great him said:
Both the ground on the plug and the bolt to the seatbelts...

So checking further that voltage drop is acceptable under load of the starter... I hooked my truck to my friends Cummins and then tried again, voltage drop was not as bad, only dropped to 11v but still no fuel. Its begging to look more and more like the pump itself is the fualt. The last couple of days the starting was very long...
Click to expand...

If the pump is at fault, then you should have battery voltage or near to it at the truck side of the fuel pump connector with the fuel pump disconnected. If you disconnect the pump and still measure low voltage on the truck side of the connector, the pump is not your problem (or at least not your complete problem).
 
Voltage was the same at the battery as at the pump plug... Both read 9.xx and then when connected to the second vehicle, they both showed 11.xx
 
IBallEngineer said:
In your original post you said battery voltage was 12.7, so now I'm confused.

:redbrick:
Click to expand...

He said cranking 9.xx, but standing 12.7. Seems about right to me, although I haven't checked cranking volts on my rig. The link below says 9.6V while cranking is normal for a 12V system. All sounds like a non-electric problem (probably the fuel pump, filter, FPR) to me. Fuel pressure test time...

Cranking Voltage Test

Further support for this at this link which is the manual for my Century 88100 Load Tester (see page 6):

http://www.cloreautomotive.com/uploaded_files/sku/365_841-731-000.pdf

A 100 Amp load test of 11.0 is the GOOD result for a typical 650 CCA 12V battery (source: dial of same Century 88100 Load Tester), and would get you a Min Cranking Volts of 9.7.

I'm calling this electric system as in perfect health. Look elsewhere.
 
Last edited:
TheDurk said:
He said cranking 9.xx, but standing 12.7. Seems about right to me, although I haven't checked cranking volts on my rig. The link below says 9.6V while cranking is normal for a 12V system. All sounds like a non-electric problem (probably the fuel pump, filter, FPR) to me. Fuel pressure test time...

Cranking Voltage Test

Further support for this at this link which is the manual for my Century 88100 Load Tester (see page 6):

http://www.cloreautomotive.com/uploaded_files/sku/365_841-731-000.pdf

A 100 Amp load test of 11.0 is the GOOD result for a typical 650 CCA 12V battery (source: dial of same Century 88100 Load Tester), and would get you a Min Cranking Volts of 9.7.

I'm calling this electric system as in perfect health. Look elsewhere.
Click to expand...

Nope, that isn't what it says.

9.6 volts or more for a 12-volt system is what it says. And for 30+ years that has been the criteria for me to condemn a battery. But I wouldn't expect my truck, your truck, or his truck to drop that low cranking. I'd say 10.5 or 11.0 at worst. I tested mine and even cranking for 15 seconds it never dropped below 11.2.

Now the reality is, I think you are right. I never use the term "standing" to describe a battery with no load, so I misunderstood.

Just sayin'

:moon:
 
Yeah I'm thinking the pump is bad. All my research and testing points to this.

That 9.7 v at time of cranking was also after a good solid 10-15 min of repeated cranking. Not continuous, but none the less a lot of cranking. I'd say at least 2min of solid continued cranking if it was all added up. So yeah I think the 9.7 v at the pump is low, but not given the situation and circumstances.

Normally I'd of had the pump swapped out by now, but I have been spending my free time looking at gx470s... This situation has made me realize that its time for a second vehicle. One that I can just put the whole family in, and drive. I need one that is nice and comfortable for long trips, and something the wife won't mind driving in bad weather. I'm gonna be retiring my 4runner to weekend warrior and inclement weather status. The gx fits all of those categorys perfectly. I'm hoping tomorrow afternoon I can drop the tank and swap the pump.

Thanks again for all your guys help here! [MENTION=102597]IBallEngineer[/MENTION], [MENTION=10169]TheDurk[/MENTION], [MENTION=49649]KidVermicious[/MENTION], and the other who helped as well.
 
Good to hear. Out of curiosity, how many miles were on the pump that failed? Thinking it might be a good time to change mine out as a preventative measure.
 
I'd like to know how many miles was on your truck when you swapped the pump. I'm having a very similar situation. So far, I've swapped the MAF and plugs, no change. I changed out the fuel filter and still nothing when I'm cranking it. Before and after I changed the fuel filter, I checked the fuel line in the engine bay close to the fuse box, and it was bone dry. Pump is getting power, but can't hear it.
 
GingerB said:
I'd like to know how many miles was on your truck when you swapped the pump. I'm having a very similar situation. So far, I've swapped the MAF and plugs, no change. I changed out the fuel filter and still nothing when I'm cranking it. Before and after I changed the fuel filter, I checked the fuel line in the engine bay close to the fuse box, and it was bone dry. Pump is getting power, but can't hear it.
Click to expand...
Sounds like a bad pump if you have power at the pump but no fuel

Sent from my XT1585 using Tapatalk
 
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