2006 Explorer

Back in the pre computer days when fuel pumps where mechanical and bolted to the side of the engine I could see this diagnosis as valid. Today's electronic fuel pumps are a very different animal and I do not believe are regulated by engine RPM, but more by fuel system regulator pressure measurements.

When was the last time you changed the fuel filter?

Steve

olutions before it starts, then runs good. Took it to a shop and everythin g checked good on the diagnostic machine. Mechanic thinks it probably a le aking check valve in the fuel line, allowing the fuel to drain back into th e tank when it sits for a while, then taking some revolutions to pump fuel back to the engine.

r a part of the fuel injection? Anyone heard of this happening? If a part of the pump, is it in the tank? Could it be replaced without pulling the tank? Any other ideas?

It's still the original filter at 75k miles. Would a reduced flow filter op erate fine at all speeds after starting?

What the mech & I both saw is not the operation of pump itself but the volu me of fluid it has to pump when it starts working. An empty line may take a couple of seconds longer than a full one. (Just thinking without knowing )

First thing is to determine IF the valve is the problem. Turn the key on for 3-5 seconds, off, and back on for 3 to 5 seconds, then back on and attempt to start. If it starts right away after that sequence you have a fuekl line pressure back-bleed somewhere. It will either be inside the fuel pump or in the FPR (Fuel pressure regulator)) Put a pressure guage on the manifold service valve and run the engine. shut it off and watch the pressure. If it drops relatively quickly,, restart the engine, shut it off and pinch off the return line from the FPR. If it holds pressure now, it is a FPD problem. If not, most likely the fuel pump (unless you have a leaky injector - which will cause the same symptoms after sitting for some time) A good dose of injector cleaner in the tank (or a motorvac treatment) could solve the problem if it is a dirty injector - and could even solve an FPR or fuel pump check valve problem. This is one case where a good "mechanic in a can" actually DOES exist and could save you a LOT of money.

The pump CAN be the issue. It is actually quite common and nowhere is there any indication the problem has anything to do with engine rpm. Even the mechanical fuel pump pressure was not at all related to engine RPM other than the fact the engine had to turn to operate the pump. Fuel pressure was a function of the strength of the spring that forced the diaphragm up after the ling from the camshaft pulled it down.

You need to understand fuel systems before commenting.

That said I'm not SURE the 2008 has an external FPR and a recirculating system - but am pretty certain the explorer had not gone to a closed constant pressure system.

A bad filter will have virtually no effect on starting, and would limit power at full throttle.

Thanks for the hint. I tried that and now wonder if it is even a fuel prob lem. I tried as you said and there was still the delay in starting. But t hen I let the engine run for about 1 minute, turned it off, and immediately restarted it. The delay was still there, 3-5 revolutions, before it caugh t. That would lead me to believe fuel could not back-leak that fast and sh ould be there.

Combustion is a mix of fuel, air, and spark. The 1st thing I did was change the air filter with a new Ford one. I had the plugs checked and was told t hey are fine and did not need to be replaced. I tried injector cleaner in 3 consecutive fill-ups. That lead me to fuel delivery, and now I'm not sure about it either. If the diagnostic checks at the repair shop didn't see any thing, and my efforts are nil, I'm scratching my head (& ass).

I'm suspicious you may have a failing crank position sensor.

I'm sure you know better than all of us. Please continue.

Well, I have been a mechanic since 1969.

Thanks for the hint. I tried that and now wonder if it is even a fuel problem. I tried as you said and there was still the delay in starting. But then I let the engine run for about 1 minute, turned it off, and immediately restarted it. The delay was still there, 3-5 revolutions, before it caught. That would lead me to believe fuel could not back-leak that fast and should be there.

Combustion is a mix of fuel, air, and spark. The 1st thing I did was change the air filter with a new Ford one. I had the plugs checked and was told they are fine and did not need to be replaced. I tried injector cleaner in 3 consecutive fill-ups. That lead me to fuel delivery, and now I'm not sure about it either. If the diagnostic checks at the repair shop didn't see anything, and my efforts are nil, I'm scratching my head (& ass).

snipped-for-privacy@snyder.on.ca wrote in news: snipped-for-privacy@4ax.com:

yes it will, I have seen it many times. change the fuel filter first and then see if the symptoms still persist. KB

If the filter is affecting starting it will DEFINITELY also cause loss of power at full throttle..

Just think - at idle and startup it only needs a small fraction of the fuel flow required at full throttle. The filter has no effect on the amount of fuel that stays in the fuel line, and with the lines full the pressure rises immediately to running pressure - and the FACT that he has experienced the same hard start after cycling the pump PROOVES it is not a fuel delivery problem.

I spent many years as a mechanic and EFI troubleshooter.

Now - an interesting observation. I have a 1996 4.0 liter Ranger with standard transmission. If I start the engine using the starter it virtually always takes between 2 and 3 turns before it fires, but if I roll it down the driveway and pop the clutch in gear it ALWAYS starts on the first 1/4 to1/2 turn of the engine (or less) The engine barely turns and it is running..

snipped-for-privacy@snyder.on.ca wrote in news:cl751bt0mivo65vq473ig9cvtinme6qdos@

This is true, but most people don`t use heavy throttle on a daily basis and will notice the hard starting first.

that is not entirely true as the comp will not turn on the injectors untill it reaches a min. fuel pressure which a restricted fuel filter will delay that event.

The filter has no effect on the

I agree his problem is probably not fuel related. I just wanted to stress that a restricted fuel filter can cause that symptom, as I have seen several time for the others following this thread. When in dought change the filer first. KB

starter draging the starting voltage to the min. mabey? those are not great starters on those to begin with. KB

There is nothing in the code that reads the fuel pressure and starts the injectors only after fuel pressure builds - the injectors will fire with no fuel pressure. They just won't squirt much. The injectors will fire even if you are out of fuel or the fuel pump has failed.

No problem with sagging voltage - it has to do with the starting algorithym in the computer. You bypass that when you don't use the starter.

snipped-for-privacy@snyder.on.ca wrote in news: snipped-for-privacy@4ax.com:

then they changed the code, because it used to be a min fuel pressure had to be present for the comp to go to run mode, it would shut down the ign when too low a pressure was detected. Point in fact, the early chev FI when the pump would get weak it would not start if fuel pressure went below I think it was 36 Lbs. KB

If the pressure was too low the injector could not supply enough fuel to start the engine, but the ignition and njectors both fired.