Starting issues

[BOB MARLIN]

I've looked through a bunch of posts and it seems to be a somewhat common problem, but the post always end before it is solved.
1990 5.0
It won't start with out starting fluid. Fuel pump runs constantly. Most posts I read pointed to bad caps on the computer, so I replaced the caps.
Fuel pump still doesn't shut off, but it will start if you floor it while turning it over and seems to run just fine once started. So what is the fuel pump looking for to shut off ?. Is it waiting for a pressure reading or is it looking for a time delay ?. I've also read that flooring it clears a flooded issue and allows it to start. It looks to have a new fuel pressure regulator on it so could this symptom be caused by the relay or maybe the ect ?. If the injectors were leaking or stuck wouldn't it run like crap after it started ?. To me, the fuel pump running is a big clue that something is not producing the signal its looking for to shut off, I just don't know where that signal needs to come from.

 

[johnnyreb]

I've looked through a bunch of posts and it seems to be a somewhat common problem, but the post always end before it is solved.
1990 5.0
It won't start with out starting fluid. Fuel pump runs constantly. Most posts I read pointed to bad caps on the computer, so I replaced the caps.
Fuel pump still doesn't shut off, but it will start if you floor it while turning it over and seems to run just fine once started. So what is the fuel pump looking for to shut off ?. Is it waiting for a pressure reading or is it looking for a time delay ?. I've also read that flooring it clears a flooded issue and allows it to start. It looks to have a new fuel pressure regulator on it so could this symptom be caused by the relay or maybe the ect ?. If the injectors were leaking or stuck wouldn't it run like crap after it started ?. To me, the fuel pump running is a big clue that something is not producing the signal its looking for to shut off, I just don't know where that signal needs to come from.

It might be the new regulator. I bought a Mr Gasket and it wasn,nt any good. Alot of these NEW PARTS are junk.

 

[BOB MARLIN]

I bought this Bronco a few months ago. It had been sitting for 17 years and I am going through it trying to get it road worthy. It's proving to be quite a challenge. Lots of "little" things wrong with it. Replaced the fuel tank last weekend. I would like to find the guy that invented the nylon fuel line for these rigs and punch him in the nose.

 

[johnnyreb]

I bought this Bronco a few months ago. It had been sitting for 17 years and I am going through it trying to get it road worthy. It's proving to be quite a challenge. Lots of "little" things wrong with it. Replaced the fuel tank last weekend. I would like to find the guy that invented the nylon fuel line for these rigs and punch him in the nose.

I went to a parts store the other day. To get some nylon hose. For 10 feet they asked me $46. I flew off and told him what to do with it. I bought 20 feet ay Lowe,s home improvement for a little over $6. If you,ll notice.They,ll tell you it will take a few days. They have to order it. They buy off the internet like you and I but want to hold a person up.

 

[Tiha]

When you hold the pedal to the floor it shuts the fuel off and injectors do not add any more. You do that to clear the engine.

Fuel pump should shut off. You need to find the fuel pump relay. Unplug it.
With the key off it should only have power to one terminal. If it has power to 2 terminals then you have some wires melted together or still have a bad ECM
If you only have power to one terminal it could very well be just a bad relay that has welded itself closed.

 

[BOB MARLIN]

This is the exact info I was looking for.
So the fuel relay receives its signal from ECM, not the FPR or the ECT correct ?. The ECM is sending the signal to the fuel relay based on an "on time" or a pressure reading from something right ?.

If the relay is bad, causing the pump to run, will the pump flood the engine by its self ?.

If the "pump on" and the "flooded" condition are separate issues what is telling the ECM to add to much fuel while cranking ?.

 

[Tiha]

It shouldn't, but there could easily be an injector leaking a little. As long as it sat I am sure there is some varnish that needs to be cleaned out of the fuel system.

 

[BOB MARLIN]

How long should the fuel rail hold pressure after everything is turned off ?.

 

[miesk5]

Yo Bob,

EEC Relay (BROWN Connector, next GREEN FP Relay Connector Under hood behind air cleaner assy) in a 90 and all up to 91
Source: by Need4racin (The 90 Bronco, Dean)


FPR PIC ON FUEL RAIL, driver side, near firewall;

 

[miesk5]

Yo Bob,
I overwrote the below because adding images seem to do that.
Fuel Pump Runs w/Ignition Switch Off; "...The relay probably has the points welded. Here is a diagram of the circuit..."
Source: by our later friend and guru, Seabronc (Rosie, Fred W) at Ford Bronco Zone Forums

Inspect AND TEST EEC & FP Relays;
Fuel Pump Relay Socket Corrosion Info; "...if you had corrosion in your relay socket, then you probably have it other places. one at a time unplug all relays and connectors on that fender and spray them down with contact cleaner. then after you let that do it's job for about 30min-1hr, go back and unplug each relay and connector again (one at a time) this time put them together with di-electric grease. you can buy a tube of it from any electrical/electronics supply or auto store. make sure you get everything plugged back in..." by detrimental

Part 1 -How to Test the Ford Fuel Pump Relay (Green Connector)
Testing The Ford EEC Power Relay (Brown Connector)

 

[Tiha]

How long should the fuel rail hold pressure after everything is turned off ?.

That really isn't all that important. In theory it will hold pressure for months. In reality at least a few seconds would be great.

 

[BOB MARLIN]

I thought maybe it would be an indicator that the injectors were leaking if it didn't hold pressure.

 

[johnnyreb]

That really isn't all that important. In theory it will hold pressure for months. In reality at least a few seconds would be great.

Tiha, now I know very little about fuel injection. About as good as I can spell it. Isn,t it the PRESSURE that keep the gas in the line---- held buy pressure-like a valve so it won,t bleed off?

 

[Tiha]

You have 3 things that keep pressure in the fuel rail. Pressure regulator, injectors and check ball in the fuel pump.

Fuel pump check ***** fail or work intermittently all the time. Not a reason to replace the pump though, unless you have dual tanks, but the pump should produce enough flow that even if the rail is low on pressure it will only take an extra second or two for the fuel pump to bring the pressure back up.

Pressure regulator has a spring in it set to the desired pressure, and pressure over that setting is returned to the tank.

Then the fuel injectors. Yes they can leak. Doesn't happen very often though, especially on an engine that is daily driven and fed clean fuel.

If the system is not holding pressure,
Cycle key to charge the system. Pinch off Fuel supply line. That will test the check ball in the fuel pump.
If pressure still falls, charge the system again, now this time you have to pinch off the pressure and return line.
If pressure still falls you have a leaky injector.
If it holds pressure the regulator is bad.

 

[johnnyreb]

You have 3 things that keep pressure in the fuel rail. Pressure regulator, injectors and check ball in the fuel pump.

Fuel pump check ***** fail or work intermittently all the time. Not a reason to replace the pump though, unless you have dual tanks, but the pump should produce enough flow that even if the rail is low on pressure it will only take an extra second or two for the fuel pump to bring the pressure back up.

Pressure regulator has a spring in it set to the desired pressure, and pressure over that setting is returned to the tank.

Then the fuel injectors. Yes they can leak. Doesn't happen very often though, especially on an engine that is daily driven and fed clean fuel.

If the system is not holding pressure,
Cycle key to charge the system. Pinch off Fuel supply line. That will test the check ball in the fuel pump.
If pressure still falls, charge the system again, now this time you have to pinch off the pressure and return line.
If pressure still falls you have a leaky injector.
If it holds pressure the regulator is bad.

Thanks alot Tiha,don,t laugh at me. I also have a 2001 Ram and I,ve changed the pump twice (New Charter) and a few days later starts all over. It ,ll crank forever before it starts. I have my cousin help me check it out he knows about fuel injection--I,m old school. Again thanks alot. Oh when it sits just for a little while it does it and sometimes it starts right up.

 

[johnnyreb]

Thanks alot Tiha,don,t laugh at me. I also have a 2001 Ram and I,ve changed the pump twice (New Charter) and a few days later starts all over. It ,ll crank forever before it starts. I have my cousin help me check it out he knows about fuel injection--I,m old school. Again thanks alot. Oh when it sits just for a little while it does it and sometimes it starts right up.

Thanks alot Tiha,don,t laugh at me. I also have a 2001 Ram and I,ve changed the pump twice (New Charter) and a few days later starts all over. It ,ll crank forever before it starts. I have my cousin help me check it out he knows about fuel injection--I,m old school. Again thanks alot. Oh when it sits just for a little while it does it and sometimes it starts right up.

Now what do you mean cycle key? I,m not up on this electronic stuff. I read to re-set the computer. Is to unhook the battery for a little while. I tried that and it seemed to help a little.

 

[BOB MARLIN]

That makes sense to me and gives me something else to check.
So, with the information here so far, is it safe to assume I actually have two separate problems that I originally thought were related but are not ?.

So key on engine off, the pump just runs. Key off engine off it does not. Fuel rail has pressure between 35-40. The pump running has nothing to do with the engine flooding.

Things that cause the engine to flood have nothing to do with turning off the fuel pump. Bad injectors, bad ECT or just a bad ECC can cause flooding.

Bad EEC or bad fuel pump relay can cause the fuel pump to run. And because I have good fuel pressure, the FPR is not the culprit. If it was a bad relay wouldn't the fuel pump just run even with the key out of the truck ?.

Bad EEC seems to be the only common component here. But that would mean two separate parts of the EEC are bad at the same time.

I'm really trying to get a good understanding on how this system works before I go throwing parts at it. Please correct my train of thought above if I have it wrong. I really appreciate the help.

 

[johnnyreb]

Now what do you mean cycle key? I,m not up on this electronic stuff. I read to re-set the computer. Is to unhook the battery for a little while. I tried that and it seemed to help a little.

How often should fuel injectors be replaced?

 

[Tiha]

Correct, 2 separate problems.

If your fuel pump shuts off with key, then yes not a bad relay.
running pump should not flood the engine.

ECT is one that I always go to as well. It can certainly flood an engine. I think the map sensor will as well.

I know the ECT when you unplug it, it defaults to a value like 40 degrees so you can just unplug it and try to start it.
Not sure what the MAP sensor defaults too but I would try it as well.

Being a 1990, I honestly don't remember how much control the O2 sensors have. I know they could prevent starting as well. But I think that was older models.

It is easy to jump to the EEC and we do see people have failures all the time but I personally have never had one fail. So just because we see it on the internet don't assume that happens to everyone. Do diligence and make the best informed decision you can. Which I guess is why you are here.

Currently you don't know if the engine is flooding with the key on engine off, or while cranking.

How is your oil level? It isn't over full is it? That can cause similar issues.

 

[Tiha]

How often should fuel injectors be replaced?

That is a topic open for debate. I for one don't replace them until there is a problem and since the early 90's not seen an injector fail. Never had a ford injector fail.
Countless trucks I have had over 200k on factory injectors. trucks that sat for years, fuel tanks that looked like coral reefs inside. Plenty of fuel pump failures from sitting and never and injector.

On the other hand people claim replacing them 80-150k miles improves performance and fuel mileage. I am sure it could make a difference. I personally don't believe you could measure the difference by seat of the pants feel or even MPG would be small. But that is what they believe and I support them.
With fuel and fuel filters today it is so hard to get any type of contaminants to the injectors it is hard to imagine they will ever plug, so that means electrical or mechanical failure and that is just not common anymore.

In a situation like this thread I can totally see injectors being gummed up with tar and varnish from sitting which is an okay reason to change them. On the other hand just about any fuel system cleaner will clean them right up if you can get it running long enough. that is the easiest thing to clean from injectors.