What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

4X4HIGH, got a question.

Fordum

Fordum

1 ton status
 Premium
Joined
Jul 31, 2008
Posts
11,474
Reaction score
2,318
Location
Fl
You would be one of the most likely to know if this would work off the top of your head.
As you know, I'm a Ford guy, so I don't have much hands on experience with TBI.
Worked on a few, but not lately, and not in depth.

But I am always looking for ways to diagnose problems easier.

I have seen many times when an engine starts running out of steam at higher RPMs due to fuel starvation. Bad fuel pump, stopped up filter, etc.

On a Ford with fuel injection, I just hang a pressure gauge on the Schrader valve on the fuel rail and watch for pressure drop when the engine revs up.

TBI don't have that option.
Someone here asked about pressure on the return line, and you told them since it was an open line back to the tank, there was no pressure to speak of.

But, it started me to thinking. What about fuel flow on the return line?

If the fuel delivery system is doing its job, there should always be an excess of fuel being delivered to the system. If someone was having problems with the engine cutting out when passing, or things like that, how hard would it be to take the return line loose, put on a short piece of hose and run it into a can or jar to see how much is flowing?

Of course a bad regulator would allow a lot to flow, but not have enough pressure to let the injectors function properly. But, even then you would know that the fuel system is supplying enough.

And I suppose that if it started cutting out with plenty of return flow, you could slightly pinch the return line to see if it evened out with more pressure..........

Just a thought. It might be easier than installing a pressure port.
 
I would never attempt such a thing since you would have hot exhaust manifolds and all it would take is once to have fuel hit the hot manifold and start a huge fire. You could pretty check the fuel pump the same way as you would a mechanical pump for volume by disconnect the fuel inlet line and jumpering the red wire hanging from the relay and see how much volume you get in X amount of time. I don't know where to find the required volume chart but i'm sure it's in a manual somewhere.

It would be best though to install a pressure test port on the fuel inlet side this way you can check for pressure at any speed/rpm.
 
4X4HIGH said:
I would never attempt such a thing since you would have hot exhaust manifolds and all it would take is once to have fuel hit the hot manifold and start a huge fire. You could pretty check the fuel pump the same way as you would a mechanical pump for volume by disconnect the fuel inlet line and jumpering the red wire hanging from the relay and see how much volume you get in X amount of time. I don't know where to find the required volume chart but i'm sure it's in a manual somewhere.

It would be best though to install a pressure test port on the fuel inlet side this way you can check for pressure at any speed/rpm.
Click to expand...

Wasn't sure where the line was in relation to the rest of the engine. I was thinking it was far enough back that it could be routed safely.

I agree that the pressure port is the way to go, but from reading things here, I was looking for an easier way than buying a kit and installing it.

Of course, I am not sure how much trouble that is, so......

Just as an aside, I had a mechanical pump on a Ford Pinto carburetor engine that would pass the flow test with flying colors.
But if you punched it to pass a car, the darn thing would die about half way past it.
Lots of fun.

Finally rigged it up to do a pressure test, and had almost 0 PSI. I replaced it and ate the core charge. I wanted to know how it passed the flow and not the pressure.
The intake and output valves inside were little press in modules. One of them, I think the intake, had popped out and was just barely sitting in the hole.
As long as there was no load, it would pump. With the slightest load, the fuel just moved back and forth from the tank.

Taught me that flow is not any good unless you have enough pressure to move it along.

Thanks for the reply.
 
Correct me if I'm wrong but the fuel pressure gauge at the filter should diagnose a lot. If your regulator is bad , even though the pumps flowing there won't be pressure do to the regulator allowing excess flow.
You could test it under load by chocking the tires. Propping the gauge do you could read it from not being under the truck. Then have somebody power brake. Watch to see if the pressure drops.
On the same note, if your filter is clogged you should show an excess in pressure if the gauge is before it in flow.
 
Yep, but the problem as I understand it, is that the trucks did not come with any kind of pressure test port.
You have to buy a kit and install one to check the pressure.

That was why I was asking about the return line flow. I was looking for a way you could get an idea if you had a delivery problem without much trouble or expense.

Pressure ports are always the way to go, but I always run into trouble on Sunday night about midnight when nothing is open.

Scott does more work on these systems in a week than I will probably do the rest of my life, so I use him for my oddball ideas.......
 
that guy on ebay is a price devil :angry1:

guys on other forums have found that same adaptor and gauge for about the same price as just his adfaptor he buys in massive bulk and marks up way to much.

here is the cheepest i have found of the one most all of us use here. http://coloradok5.com/forums/showthread.php?t=291856 and 11 bucks cheeper than cfm tech price.
 
You must log in or register to reply here.

Latest Posts

Top Bottom