Intermittent fuel pump issues with a 1987 ford ranger

[RustyDusty]

Rusty,

Does it start with starter fluid shot into the trottle body? That is the 50/50 test; it tells if you have a fuel.or a spark issue.

I will try starting it with starter fluid next time it won’t start. I’m pretty sure it will start because the truck runs great whenever the fuel pump turns on. It’s when the fuel pump doesn’t turn on that it won’t run.

I tried jiggling the TFI wires and couldn’t get the the fuel pump to do anything unusual. Seems like the fuel pump only acts up after it’s been driven a bit. Which sounds so much like an overheated TFI module but we did already move it away from the distributor.

 

[Shran]

Don't rule out a bad in tank pump even if it looks new... For several years I was getting maybe 6 months out of those in one particular truck. They would fail, the high pressure pump would still suck fuel though it but would overheat and lock up. After a cool off period it would start working again. I haven't had that problem in a while so maybe pump quality has improved but it's still possible.

 

[RustyDusty]

Don't rule out a bad in tank pump even if it looks new... For several years I was getting maybe 6 months out of those in one particular truck. They would fail, the high pressure pump would still suck fuel though it but would overheat and lock up. After a cool off period it would start working again. I haven't had that problem in a while so maybe pump quality has improved but it's still possible.

I see, so you're saying its possible the reason why the high pressure fuel pump doesnt turn on sometimes is because it's working overtime if the in-tank pump is failing causing the high pressure pump to overheat and lock up for a certain amount of time? I will keep that in mind when investigating further.

 

[Shran]

I see, so you're saying its possible the reason why the high pressure fuel pump doesnt turn on sometimes is because it's working overtime if the in-tank pump is failing causing the high pressure pump to overheat and lock up for a certain amount of time? I will keep that in mind when investigating further.

Yes, exactly. Probably somewhat unlikely but it did happen to me several times.

 

[bobbywalter]

Yeah post number 9.

 

[Cees Klumper]

I am having a similar issue, with the fuel pump not getting energized on colder (mid-sixties) mornings. Once it gets warmer, it starts fine, won't stall while drivinv and will re-start every time. I tried a new fuel pump relay and jiggling the ignition module wires but what seems to have fixed it (knock on wood) was swapping the ECU - three days of cold morning starts without a problem. Maybe a capacitor on the circuit board going out. If it happens again, I plan to drop the tank to look at the fuel pump connecting wires etc. The PO did replace the fuel pump (only one pump on this truck, a '90 Bronco II) maybe two years ago, but we know parts can fail that quickly.

 

[Paulos]

I am having a similar issue, with the fuel pump not getting energized on colder (mid-sixties) mornings. Once it gets warmer, it starts fine, won't stall while drivinv and will re-start every time. I tried a new fuel pump relay and jiggling the ignition module wires but what seems to have fixed it (knock on wood) was swapping the ECU - three days of cold morning starts without a problem. Maybe a capacitor on the circuit board going out. If it happens again, I plan to drop the tank to look at the fuel pump connecting wires etc. The PO did replace the fuel pump (only one pump on this truck, a '90 Bronco II) maybe two years ago, but we know parts can fail that quickly.

I once had a similar problem, but the temps were colder (in the winter). Three days in a row I tried starting my Ranger to go to work, but it wouldn't start. While trying to figure out what the problem was, the sun rose and warmed things up a bit. It would then start and run normal until the following morning. I traced the problem to the inertia switch, bypassed it, and have not had the problem since (7 years now).

 

[Cees Klumper]

Thanks - I tested the inertia switch by jumping it but still no start. Bet yes that's another possible cause.

 

[TonyEV]

So today we were on our way home in the truck and while turning a corner the truck died and I rolled into a parking spot, put it in park and took out the multimeter. I didn't have a way of connecting the multimeter directly to the high pressure fuel pump while the pump was plugged in so I just tapped into the inertia switch and had my girlfriend turn the key to prime the pump. I heard the pump prime so I had her try a few times, it primed each time and I was getting 12v so instead of waiting around for it to not work we just started the engine. I kept watching the multimeter hooked up to the inertia switch with the engine running waiting to see if the engine would die again. It was pretty steady at around 13.7v until it jumped to over 14v at the exact moment the idle dropped so low it alllllmost died but it caught its breath and went back to idling normally, the voltage was back to 13.7v. My best guess of what happened there is the high pressure fuel pump crapping out for a sec and relieving the electrical system of its energy draw spiking the voltage to over 14v until the pump kicked back in and brought the voltage back down to 13.7v and saved the engine from stalling. Curious to hear anyone else's thoughts on this. I'm fairly convinced that despite the pump appearing to be pretty new that it's failing and needs to be replaced. I'll replace the fuel filter as well. I don't know the state of the gas tank interior unfortunately. Is it possible for crud in an old gas tank to choke the high pressure fuel pump enough for it to not even turn on sometimes but work fine at other times? I feel like at this point the pump is the obvious answer here, I just don't like to throw parts at a truck before actually understanding what's wrong with it. Thanks!

So today we were on our way home in the truck and while turning a corner the truck died and I rolled into a parking spot, put it in park and took out the multimeter. I didn't have a way of connecting the multimeter directly to the high pressure fuel pump while the pump was plugged in so I just tapped into the inertia switch and had my girlfriend turn the key to prime the pump. I heard the pump prime so I had her try a few times, it primed each time and I was getting 12v so instead of waiting around for it to not work we just started the engine. I kept watching the multimeter hooked up to the inertia switch with the engine running waiting to see if the engine would die again. It was pretty steady at around 13.7v until it jumped to over 14v at the exact moment the idle dropped so low it alllllmost died but it caught its breath and went back to idling normally, the voltage was back to 13.7v. My best guess of what happened there is the high pressure fuel pump crapping out for a sec and relieving the electrical system of its energy draw spiking the voltage to over 14v until the pump kicked back in and brought the voltage back down to 13.7v and saved the engine from stalling. Curious to hear anyone else's thoughts on this. I'm fairly convinced that despite the pump appearing to be pretty new that it's failing and needs to be replaced. I'll replace the fuel filter as well. I don't know the state of the gas tank interior unfortunately. Is it possible for crud in an old gas tank to choke the high pressure fuel pump enough for it to not even turn on sometimes but work fine at other times? I feel like at this point the pump is the obvious answer here, I just don't like to throw parts at a truck before actually understanding what's wrong with it. Thanks!

Back to 13.7v? Seems loose connection