1991 Lariat 5.0 no start
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1991 Lariat 5.0 no start
Hi all. First off I love my Ford. Any way I bought a 1991 F150 about a year and a half ago with 70000 miles. she doesnt seem to have been abused but does sit alot. any way last couple times i had it running the check engine light came off it ran a little rough then ran fine and light went out. A couple of weeks ago I started it to let it warm up. it idles a little rough but idled nonetheless and it started running rough and died. it started again and then acted like it wanted to die and i tried to rev engine and no power then it died. i got it started and it ran ok. Last weekend it would not start. The fuel pump has a high pitch noise but not sure if that is issue. thats a big expensive project. is that where I start? How do I test? Is this the wrong place to start? i want to get it rolling for.my daughter but do not have mechanic money 
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bummer. battery may have gone dead i dont know. i charged it when starter drug it down. so i guess i have do process of elimination now. ughh.
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i followed Youtube video so pretty sure i did it correctly. it show over a 1/4 Tank and i have not had problems with the guage but i think i will add gas just to be safe. i could be out of gas. i think thats unlikely though. i will start with filter. alhough it acted like a fuel pump issue.
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Test fuel pressure first. You can buy a test unit at Harbor Freight that works good enough that costs 20 bucks.
http://www.harborfreight.com/fuel-in...ter-92699.html
That's where you start on these. You may also have bad gas that has separated and won't pump. Adding more gas means the tank is going to be even more heavy to remove. Test for pressure first.
If fuel pressure is okay-40 lbs as I remember, then there are several things to check with the ignition side. That engine probably has the TFI or Thin Film Ignition in the dizzy. That thing can give you all kinds of grief as it works great ....sometimes and then doesn't work worth squat. Most commonly it works fine until the unit gets hot but that's no guarantee. Check the contacts in the dizzy cap. If you have a cheap cap with aluminum contacts, replace it with one that has brass contacts, the aluminum sucks and burns quick. Check the plug wires with an ohm meter. Pull the plugs and check them for color. There are charts on the net to tell you what is happening with the color on the plugs.
You can also have vacuum leaks that can cause erratic running. You can pretty much cut the main users out of the system at the intake manifold tree. The brake booster is the biggest user and a cracked or broken diaphragm in one can be a real headache.
Your engine most likely has a MAP sensor. My 91 Bronco 5.0 sits on the firewall just above the heater. It has a vacuum line and an electrical plug on it. To clean the injectors, run the engine at 2000 rpms prox and disconnect the vacuum line. The injectors will run wide open. I'd suggest having a fuel system cleaner in the gas like Techron while doing this. Only run it for no more than 20 seconds otherwise the exhaust starts filling with unburned gas. That can be hard on the cats. If you pull the vacuum line and nothing changes, the sensor is bad or the vacuum line is bad.
If you end up having to pull the gas tank, it's not really that hard. I dropped my Bronco last fall by myself and it took about an hour down and about an hour and a half back up. If you drop it, replace the fuel pump and fuel gauge sending unit with Motorcraft parts ONLY. Yeah, they're more money but they work where others might not and then you get to drop the tank again. Also check 2 other items. The fuel pump has a fuel pump relay that is on the drivers side of the engine bay by the air filter. Check it for voltage going thru it. Then check and by-pass the inertia switch which is under the dash. This little headache is a pain to get to. It's above the brake pedal on the inside against the firewall. It will have a red reset button on it that you push in from the top to reset. These are a known headache that can cause intermittent electrical issues at the fuel pump. Because the POS costs close to 100 bucks, I by-passed mine which is easy to do by cutting the end off of the clip and wiring it together. Yeah, if I'm in a bad wreck the fuel pump might not shut down and there be a dandy fire. I've lived thru worse.
These are a few things you can check but the first thing is fuel pressure. Start there and expand out as needed.
http://www.harborfreight.com/fuel-in...ter-92699.html
That's where you start on these. You may also have bad gas that has separated and won't pump. Adding more gas means the tank is going to be even more heavy to remove. Test for pressure first.
If fuel pressure is okay-40 lbs as I remember, then there are several things to check with the ignition side. That engine probably has the TFI or Thin Film Ignition in the dizzy. That thing can give you all kinds of grief as it works great ....sometimes and then doesn't work worth squat. Most commonly it works fine until the unit gets hot but that's no guarantee. Check the contacts in the dizzy cap. If you have a cheap cap with aluminum contacts, replace it with one that has brass contacts, the aluminum sucks and burns quick. Check the plug wires with an ohm meter. Pull the plugs and check them for color. There are charts on the net to tell you what is happening with the color on the plugs.
You can also have vacuum leaks that can cause erratic running. You can pretty much cut the main users out of the system at the intake manifold tree. The brake booster is the biggest user and a cracked or broken diaphragm in one can be a real headache.
Your engine most likely has a MAP sensor. My 91 Bronco 5.0 sits on the firewall just above the heater. It has a vacuum line and an electrical plug on it. To clean the injectors, run the engine at 2000 rpms prox and disconnect the vacuum line. The injectors will run wide open. I'd suggest having a fuel system cleaner in the gas like Techron while doing this. Only run it for no more than 20 seconds otherwise the exhaust starts filling with unburned gas. That can be hard on the cats. If you pull the vacuum line and nothing changes, the sensor is bad or the vacuum line is bad.
If you end up having to pull the gas tank, it's not really that hard. I dropped my Bronco last fall by myself and it took about an hour down and about an hour and a half back up. If you drop it, replace the fuel pump and fuel gauge sending unit with Motorcraft parts ONLY. Yeah, they're more money but they work where others might not and then you get to drop the tank again. Also check 2 other items. The fuel pump has a fuel pump relay that is on the drivers side of the engine bay by the air filter. Check it for voltage going thru it. Then check and by-pass the inertia switch which is under the dash. This little headache is a pain to get to. It's above the brake pedal on the inside against the firewall. It will have a red reset button on it that you push in from the top to reset. These are a known headache that can cause intermittent electrical issues at the fuel pump. Because the POS costs close to 100 bucks, I by-passed mine which is easy to do by cutting the end off of the clip and wiring it together. Yeah, if I'm in a bad wreck the fuel pump might not shut down and there be a dandy fire. I've lived thru worse.
These are a few things you can check but the first thing is fuel pressure. Start there and expand out as needed.
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Junior Member
Joined: Jan 2015
Posts: 9
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Test fuel pressure first. You can buy a test unit at Harbor Freight that works good enough that costs 20 bucks.
http://www.harborfreight.com/fuel-in...ter-92699.html
That's where you start on these. You may also have bad gas that has separated and won't pump. Adding more gas means the tank is going to be even more heavy to remove. Test for pressure first.
If fuel pressure is okay-40 lbs as I remember, then there are several things to check with the ignition side. That engine probably has the TFI or Thin Film Ignition in the dizzy. That thing can give you all kinds of grief as it works great ....sometimes and then doesn't work worth squat. Most commonly it works fine until the unit gets hot but that's no guarantee. Check the contacts in the dizzy cap. If you have a cheap cap with aluminum contacts, replace it with one that has brass contacts, the aluminum sucks and burns quick. Check the plug wires with an ohm meter. Pull the plugs and check them for color. There are charts on the net to tell you what is happening with the color on the plugs.
You can also have vacuum leaks that can cause erratic running. You can pretty much cut the main users out of the system at the intake manifold tree. The brake booster is the biggest user and a cracked or broken diaphragm in one can be a real headache.
Your engine most likely has a MAP sensor. My 91 Bronco 5.0 sits on the firewall just above the heater. It has a vacuum line and an electrical plug on it. To clean the injectors, run the engine at 2000 rpms prox and disconnect the vacuum line. The injectors will run wide open. I'd suggest having a fuel system cleaner in the gas like Techron while doing this. Only run it for no more than 20 seconds otherwise the exhaust starts filling with unburned gas. That can be hard on the cats. If you pull the vacuum line and nothing changes, the sensor is bad or the vacuum line is bad.
If you end up having to pull the gas tank, it's not really that hard. I dropped my Bronco last fall by myself and it took about an hour down and about an hour and a half back up. If you drop it, replace the fuel pump and fuel gauge sending unit with Motorcraft parts ONLY. Yeah, they're more money but they work where others might not and then you get to drop the tank again. Also check 2 other items. The fuel pump has a fuel pump relay that is on the drivers side of the engine bay by the air filter. Check it for voltage going thru it. Then check and by-pass the inertia switch which is under the dash. This little headache is a pain to get to. It's above the brake pedal on the inside against the firewall. It will have a red reset button on it that you push in from the top to reset. These are a known headache that can cause intermittent electrical issues at the fuel pump. Because the POS costs close to 100 bucks, I by-passed mine which is easy to do by cutting the end off of the clip and wiring it together. Yeah, if I'm in a bad wreck the fuel pump might not shut down and there be a dandy fire. I've lived thru worse.
These are a few things you can check but the first thing is fuel pressure. Start there and expand out as needed.
http://www.harborfreight.com/fuel-in...ter-92699.html
That's where you start on these. You may also have bad gas that has separated and won't pump. Adding more gas means the tank is going to be even more heavy to remove. Test for pressure first.
If fuel pressure is okay-40 lbs as I remember, then there are several things to check with the ignition side. That engine probably has the TFI or Thin Film Ignition in the dizzy. That thing can give you all kinds of grief as it works great ....sometimes and then doesn't work worth squat. Most commonly it works fine until the unit gets hot but that's no guarantee. Check the contacts in the dizzy cap. If you have a cheap cap with aluminum contacts, replace it with one that has brass contacts, the aluminum sucks and burns quick. Check the plug wires with an ohm meter. Pull the plugs and check them for color. There are charts on the net to tell you what is happening with the color on the plugs.
You can also have vacuum leaks that can cause erratic running. You can pretty much cut the main users out of the system at the intake manifold tree. The brake booster is the biggest user and a cracked or broken diaphragm in one can be a real headache.
Your engine most likely has a MAP sensor. My 91 Bronco 5.0 sits on the firewall just above the heater. It has a vacuum line and an electrical plug on it. To clean the injectors, run the engine at 2000 rpms prox and disconnect the vacuum line. The injectors will run wide open. I'd suggest having a fuel system cleaner in the gas like Techron while doing this. Only run it for no more than 20 seconds otherwise the exhaust starts filling with unburned gas. That can be hard on the cats. If you pull the vacuum line and nothing changes, the sensor is bad or the vacuum line is bad.
If you end up having to pull the gas tank, it's not really that hard. I dropped my Bronco last fall by myself and it took about an hour down and about an hour and a half back up. If you drop it, replace the fuel pump and fuel gauge sending unit with Motorcraft parts ONLY. Yeah, they're more money but they work where others might not and then you get to drop the tank again. Also check 2 other items. The fuel pump has a fuel pump relay that is on the drivers side of the engine bay by the air filter. Check it for voltage going thru it. Then check and by-pass the inertia switch which is under the dash. This little headache is a pain to get to. It's above the brake pedal on the inside against the firewall. It will have a red reset button on it that you push in from the top to reset. These are a known headache that can cause intermittent electrical issues at the fuel pump. Because the POS costs close to 100 bucks, I by-passed mine which is easy to do by cutting the end off of the clip and wiring it together. Yeah, if I'm in a bad wreck the fuel pump might not shut down and there be a dandy fire. I've lived thru worse.
These are a few things you can check but the first thing is fuel pressure. Start there and expand out as needed.
Thread Starter
|
Junior Member
Joined: Jan 2015
Posts: 9
Likes: 0
i need help past a big problem. there is a loud humming noize coming from rear of truck that i am guessing is fuel pump, this happens even with ley removed. i read it could be green relay. maybe i have bad relay and fuel pump going out. it also is draining battery so mybe i hVe a short. should i gove up and tow to mechanic?
Thread Starter
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Junior Member
Joined: Jan 2015
Posts: 9
Likes: 0
i need help past a big problem. there is a loud humming noize coming from rear of truck that i am guessing is fuel pump, this happens even with ley removed. i read it could be green relay. maybe i have bad relay and fuel pump going out. it also is draining battery so mybe i hVe a short. should i gove up and tow to mechanic?