Ref 2006 Ford Explorer XLT, 4.0 6cyl. The engine is now making 3-5 revolut
ions before it starts, then runs good. Took it to a shop and everything ch
ecked good on the diagnostic machine. Mechanic thinks it probably a leakin
g check valve in the fuel line, allowing the fuel to drain back into the ta
nk when it sits for a while, then taking some revolutions to pump fuel back
to the engine.
So my question is where would this valve be? A part of the fuel pump or 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?
On 10/2/2015 11:47 PM, firstname.lastname@example.org wrote:
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
When was the last time you changed the fuel filter?
On Saturday, October 3, 2015 at 7:47:33 AM UTC-5, Steve Stone wrote:
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.
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
On Mon, 5 Oct 2015 14:15:18 +0000 (UTC), Kevin Bottorff
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..
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
On Tue, 6 Oct 2015 14:10:56 +0000 (UTC), Kevin Bottorff
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
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
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
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.
On Fri, 2 Oct 2015 20:47:00 -0700 (PDT), email@example.com wrote:
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.
On Saturday, October 3, 2015 at 1:05:18 PM UTC-5, Clare wrote:
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).
On Saturday, October 3, 2015 at 1:05:18 PM UTC-5, Clare wrote:
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
This fellow had the same problem. Fix was never posted but a lot of
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