Intermittent extended cranking time to start engine

[974X4BLACKSPORT]

1997 4.L OHV, This just started happening recently. Normally, engine would start consistantly in about 1 sec worth of cranking time and engine is up and running, hot or cold. However, sometimes it is taking an exxtra 2-3 sec. of cranking before it starts, usually after it has sat a couple hours. I noticed this morning it took extra crank time to start and sputterd to life instead of the normal 1 sec. cranking and starting. Everything else is normal, no codes, engine runs great.
My plans are to install my fuel pressure gauge and watch it through a day of driving and sitting time for leakdown of the fuel pressure regulator.
Any other ideas are apprieciated!

 

[koda2000]

My 2001 5.0L Expl did this for several years. Always started fine when cold, but sometimes when warm (after sitting for 45 mins or so) long crank no start. Multiple tries and eventually it would start. Finally after sitting for many weeks during the winter (garaged) it would not start at all. I wasn't hearing the fuel pump hum either. Installed a new pump and it's been starting great ever since. In my experience the fuel pumps just wear out eventually, around 175,000-200,000 miles. They all failed (two 2000 Mountaineers, two 2001 Explorers and my 2001 Sport Trac) right around this mileage. Our '97 Sport made it to 242,000, but I replaced it just to be safe.

Start by swapping the fuel pump relay, check the plug on the inertia switch and check the fuel pressure to be sure. I believe a 96 should show around 35-37 PSI at the rail. The '96 also has a fuel pressure regulator on the fuel rail.

If your fuel pressure is good the problem could be with the crank position sensor, which controls spark.

 

[974X4BLACKSPORT]

My 2001 5.0L Expl did this for several years. Always started fine when cold, but sometimes when warm (after sitting for 45 mins or so) long crank no start. Multiple tries and eventually it would start. Finally after sitting for many weeks during the winter (garaged) it would not start at all. I wasn't hearing the fuel pump hum either. Installed a new pump and it's been starting great ever since. In my experience the fuel pumps just wear out eventually, around 175,000-200,000 miles. They all failed (two 2000 Mountaineers, two 2001 Explorers and my 2001 Sport Trac) right around this mileage. Our '97 Sport made it to 242,000, but I replaced it just to be safe.

Start by swapping the fuel pump relay, check the plug on the inertia switch and check the fuel pressure to be sure. I believe a 96 should show around 35-37 PSI at the rail. The '96 also has a fuel pressure regulator on the fuel rail.

If your fuel pressure is good the problem could be with the crank position sensor, which controls spark.

Thaks for the info. and advice!

 

[imp]

Fuel pumps using the returnless system seem to last far longer, as the pumps are not running "full-bore" all the time, rather running only fast enough to maintain the regulated pressure.

With the return-type system, the pump is putting out far more flow all the time, than is needed by the engine. Back in the early days of EEC-IV, many experts recommended replacing the pump at 50,000 miles, regardless of it's condition. imp

 

[lobo411]

Sounds like my `96 OHV 2 years ago. I started noticing an extended crank time, but otherwise the vehicle ran great. I checked the fuel pressure and it was within the normal range. Then one morning...it cranked but didn't start.

I used a rubber mallet to pound on the fuel tank around where I thought the fuel pump was and cranked it again...started right up. I replaced the fuel pump and it's been working fine for the last 2 yrs.

 

[koda2000]

It can be very difficult to hear the fuel pump prime if you in a public parking lot, but if you can't hear prime (run for approx 2 secs each time the ignition key is turned to ON) I've found that repeatedly turning the key from OFF to ON may get the pump to run. I've never had any luck thumping the bottom of the tank. When my 5.0L finally wouldn't start I had to turn the key ON/OFF at least 50 times to get the FP to run so that I could move the truck to change the pump.

 

[974X4BLACKSPORT]

This morning I went out and hooked up my fuel pressure gauge, and the fuel pressure was zero, zilch, not even a drop leaked out hooking up the gauge. I turned the key "on" but not start, and the pressure went to about 20, then cycled the key again and pressure was about 35 psi, then turned the key to start and it started up normally. After a test drive to warm up the engine, I left the gauge on the fuel rail to see how long it take for the pressure to leak down. So, it looks like the fuel pressure regulator is leaking down after sitting for some time, other than that the engine runs excellent, I hope all it is is the fuel pressure regulator.

 

[koda2000]

The regulator is there to reduce pressure, not increase it. My guess is that issue is your fuel pump.

 

[imp]

The regulator is there to reduce pressure, not increase it. My guess is that issue is your fuel pump.

@koda2000

Yes, and no. The pressure regulator does just that: regulates or controls pressure within a usable range by varying the amount of fuel allowed to return to the tank. Thus, when the gas pedal is "stabbed", fuel pressure suddenly drops, the regulator instantly responds by increasing the pressure. It does that by decreasing the flow back to the tank.

Semantics, I guess. Anyway, the regulator is a relatively inexpensive part, especially if labor cost is thrown in, compared to pump replacement. Just my 2 cents. imp

 

[974X4BLACKSPORT]

Well, it's 4 hours after shutting it off after going around the block with it this morning and it has cooled down, and now as it sits "engine off", fuel pressure has dropped to zero again.

 

[koda2000]

IDK if the check-valve to hold pressure is part of the fuel pump or the FPR. The fuel pump has a short piece of submersible fuel line which connects it to the fuel line. It's held in place by 2 screw clamps. Sometimes this piece of hose can develop a small split/crack. This could cause the fuel line to lose pressure pretty quickly and/or not allow for sufficient fuel pressure. I always replace this piece of hose (and the piece after the FPR on return-less fuel systems) and replace the screw clamps with fuel-injection (FI) style clamps just to be safe. If you end up dropping the tank to investigate, there's no way I wouldn't replace the fuel pump and lines while I was in there

@imp - I agree with your stated function of the FPR, but on engine start it should not be reducing the pump's fuel pressure below about 35 PSI.

 

[974X4BLACKSPORT]

Figured it out, after much searching, it has to be the fuel pump, or related fuel hoses in the tank leaking, so I orderd a new pump/hardware kit from RA. I am going to drive it till the remaining 1/2 tank of fuel is uused up and then drop the fuel tank and fix whatever needs fixin!

FYI, RA (rockauto) has a large selection of closeout parts real cheap, I got some hood struts real cheap!
http://www.rockauto.com/RSS/vehiclefeeds.php?carcode=1119686&m=wc&l=en&html=true

Thanks ALL!

 

[imp]

IDK if the check-valve to hold pressure is part of the fuel pump or the FPR. The fuel pump has a short piece of submersible fuel line which connects it to the fuel line. It's held in place by 2 screw clamps. Sometimes this piece of hose can develop a small split/crack. This could cause the fuel line to lose pressure pretty quickly and/or not allow for sufficient fuel pressure. I always replace this piece of hose (and the piece after the FPR on return-less fuel systems) and replace the screw clamps with fuel-injection (FI) style clamps just to be safe. If you end up dropping the tank to investigate, there's no way I wouldn't replace the fuel pump and lines while I was in there

@imp - I agree with your stated function of the FPR, but on engine start it should not be reducing the pump's fuel pressure below about 35 PSI.

@koda2000
Evidently, @974X4BLACKSPORT is on the road to success. I posted my reply regarding how the FPR works not to try to make you look bad; quite the contrary. If we can work together with thoughts of all thrown together, maybe better understanding might result.

On fuel pressure and volume flow, and other effects, a lot of guys do hit and miss, which I really regret, but not all of us have had the luck to study the physics of this business.

Am glad my remarks about FPR made sense to you. Thanks for your support! imp

 

[koda2000]

@koda2000
Evidently, @974X4BLACKSPORT is on the road to success. I posted my reply regarding how the FPR works not to try to make you look bad; quite the contrary. If we can work together with thoughts of all thrown together, maybe better understanding might result.

On fuel pressure and volume flow, and other effects, a lot of guys do hit and miss, which I really regret, but not all of us have had the luck to study the physics of this business.

Am glad my remarks about FPR made sense to you. Thanks for your support! imp

@imp - No offense taken. I was speaking in general terms and about the fuel pressure at idle. I should have elaborated more.