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  #1  
Old May 5th, 2012, 09:33
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sixty7ss sixty7ss is offline
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Won't Start on First Try, Will on Second

Let me explain...

In the morning, or if my Jeep hasn't run for a while, when I turn the key the first time, it just cranks and won't start. I then have to turn the key off and try again. It always works the second time. It doesn't even hesitate. I hope that made sense.

My understanding is that this is relatively common. My mechanic thinks it's a tired starter. Any ideas?
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  #2  
Old May 5th, 2012, 09:43
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Re: Won't Start on First Try, Will on Second

This sounds like a classic problem. Try and turn the switch on for 10 seconds and then off for 10 seconds for a few times before you actually crank it.

If it then starts right up, you have a bad one way valve in the fuel pump. You can replace it with one in the fuel line.
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  #3  
Old May 5th, 2012, 10:42
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Re: Won't Start on First Try, Will on Second

What year/engine?
---------------------------------------

The check valves (there are two of them; one on the fuel pressure regulator and another on the fuel pump) are part of the fuel pump assembly on 95.5-2001 vintage 4.0 XJs. When a check valve starts to fail, it can reduce fuel pressure to a point where an extended cranking time is needed to start the engine. It is a very common failure. I experienced it on my 99 at around 75K.

A good (and simple) first step in helping you troubleshoot this problem is called “the poor mans prime”

1. Turn key to ON position (do not crank the engine!)
2. The fuel pump will energize and run for a couple of seconds
3. Turn key to OFF position
4. Repeat above steps 1-3 two more times
5. NOW crank the engine over

If the engine starts quickly and cleanly after performing this procedure, you may have a check valve issue. If it starts and runs poorly for a few seconds, it could also be a leaky fuel injector resulting in the fuel pressure leaking down and the subsequent stumble upon startup is the engine clearing the excess fuel that has leaked into the cylinder because of the faulty injector.

Also be aware that a bad battery can give you starting symptoms as well. Have your battery load tested (any parts store will do this for free) if you have any doubt; your XJ does NOT like low available battery voltage. Be sure battery connections and posts are CLEAN.

Some troubleshooting tips for extended crank times. You will need a fuel pressure gauge. Many parts stores will rent you this tool inexpensively.

*Hook up fuel pressure gauge on the schrader valve on the fuel rail under the hood

*Start engine and bring to normal operating temperature.

*Observe fuel pressure gauge. Normal operating pressure should be 49.2 psi (plus or minus 5 psi)

*Shut engine off.

*Observe pressure on gauge. Pressure should not fall below 30 psi for five minutes.

If pressure falls below 30 psi, it must be determined if a fuel injector, a check valve within the
fuel pump assembly, or a fuel tube/line is leaking. An adaptor tool/hose included with the fuel pressure gauge can help you with this. Consult the manual that comes with the fuel pressure gauge and the Factory Service Manual for your year XJ for more information on this exact procedure, but here is basically how it works:

*Turn the engine off and immediately clamp the fuel line at the adaptor hose. Watch the pressure gauge and see how long it takes to lose pressure.

*If the pressure remains at 49 psi for an extended period of time then the problem is in the tank – most likely a check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky fuel injector.

**Note. Where check valve is suspect, a quick loss of fuel pressure is often the fuel pressure regulator check valve and a slow loss of pressure is often the fuel pump check valve. But keep in mind that either or both check valves can be to blame.

You can limp a check valve problem along indefinitely if you like, as it doesn't mean the fuel pump itself is going to fail. Perform the “poor mans prime” before cranking to speed up your starts. However, if you have a check valve issue and want to resolve it, it is recommended that you replace the entire fuel pump assembly for two reasons. First, you have to drop the gas tank to access the assembly. Secondly, with two check valves, replacing just the fuel pressure regulator where one of the check valve resides may or may not resolve your problem; remember there are two check valves; the other one is on the fuel pump.

The fuel pump assembly consists of fuel pump, fuel pressure regulator, fuel gauge sending unit, fuel gauge float, pickup filter and pigtail wiring harness. If you do replace the fuel pump assembly, purchase a high quality unit; you do get what you pay for here. Some cheap aftermarket assemblies have been known to fail prematurely. I personally prefer Bosch fuel pumps as they manufacture the best fuel pump assemblies for the XJ. Carter is my second choice. Airtex is my least favorite choice and I will not recommend or install them.
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Old May 5th, 2012, 10:57
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Re: Won't Start on First Try, Will on Second

'96 and later, a secondary check valve is not a good idea. My '96 doesn't have a regulator on the fuel rail, therefore there is no way to deal with an over-pressure condition forward of the secondary check valve. It started to show the slow-to-start symptoms about a year ago, and I was warned against the second check valve because of the lack of a fuel-rail regulator. So, someday soon, I'll be replacing the fuel pump, as I have to replace the tank because now it's leaking. My '92, on the other hand, sits for months at a time, and starts right up. Go figure...

Last edited by heyhar; May 5th, 2012 at 11:02.
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  #5  
Old May 5th, 2012, 13:51
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Re: Won't Start on First Try, Will on Second

I have a 2000 w/ the 4.0L.

I can't actually limp it along because I'm putting in a remote start system and I can't have it failing to start all the time.

I appreciate all the info. That gives me plenty to check out. Thanks, guys.
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  #6  
Old May 5th, 2012, 14:16
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Re: Won't Start on First Try, Will on Second

x2 for suspecting the battery. been chasing a hard start on my 99 and have finally swapped out the battery. starts first time everytime since. suprised about this since the NAPA battery wasnt much more than a year old. my symptoms were a hard start and rough idle for a few seconds when it did start, sometimes a little throttle would help the motor catch.
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Old May 6th, 2012, 10:31
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Re: Won't Start on First Try, Will on Second

Quote:
Originally Posted by sixty7ss View Post
....My mechanic thinks it's a tired starter.
I'd find a new mechanic.... Without being there to help diagnose the problem, I'd suspect the fuel pressure regulator.

How many miles? The F/P/R is supposed to be good for about 80,000 miles.

But you really need to put a pressure gauge on the rail and start there.

With the key on and the engine off, you should have about 50 psi.

After you start the engine then shut it off, you should have at least 30 PSI after 5 minutes.

There are a whole host of other tests to determine where exactly a problem exists, but that's where you should start.
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Old May 6th, 2012, 21:07
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Re: Won't Start on First Try, Will on Second

post '96 without the return line on the fuel rail the usual suspect for this problem is the pressure relief valves on the fuel tank. there are a couple of plastic valves on top of the fuel tank that are designed to vent excess air pressure from the fuel tank into the evap canister, when they fail they cause the exact problem you are describing.
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Old May 6th, 2012, 21:29
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Re: Won't Start on First Try, Will on Second

Quote:
Originally Posted by Original_MudButt View Post
I'd find a new mechanic.... Without being there to help diagnose the problem, I'd suspect the fuel pressure regulator.

How many miles? The F/P/R is supposed to be good for about 80,000 miles.

But you really need to put a pressure gauge on the rail and start there.

With the key on and the engine off, you should have about 50 psi.

After you start the engine then shut it off, you should have at least 30 PSI after 5 minutes.

There are a whole host of other tests to determine where exactly a problem exists, but that's where you should start.
I appreciate the thought, but there's not a better mechanic on the planet. He said that based on a very poor description given by me. This guy works on everything from European imports to 18-wheelers. Not just maintenance - full blown engine rebuilds, suspension systems, everything. Down Time Automotive & Diesel, for those of you in the Phoenix Metro area of Arizona.
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  #10  
Old May 6th, 2012, 21:30
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Re: Won't Start on First Try, Will on Second

Quote:
Originally Posted by GrimmJeeper View Post
post '96 without the return line on the fuel rail the usual suspect for this problem is the pressure relief valves on the fuel tank. there are a couple of plastic valves on top of the fuel tank that are designed to vent excess air pressure from the fuel tank into the evap canister, when they fail they cause the exact problem you are describing.
Does that require replacing the fuel pump?
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  #11  
Old May 6th, 2012, 21:35
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Re: Won't Start on First Try, Will on Second

no they are just two (I believe 2 maybe 1) plastic check valves that are on top of the fuel tank, all you have to do is drop the tank. you have to get them from the dealer or an aftermarket OEM supplier, your average auto parts store will not have them.
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  #12  
Old May 7th, 2012, 04:49
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Re: Won't Start on First Try, Will on Second

There is one check valve (primary) on the regulator and one (secondary) on the fuel pump.

I recommend replacing the entire fuel pump assembly while you have the tank down.

And get a quality brand name. My favorite is Bosch, Carter is my second choice. Do NOT buy an Airtex; they are offered at many parts stores as a low price point, but SEARCH to see the luck people have had with them. I won't install one or recommend one.
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Old May 7th, 2012, 06:39
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Re: Won't Start on First Try, Will on Second

Unless it's a leaky injector.... As I said before, there is a host of diagnosis procedures to find the culprit....
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Old May 7th, 2012, 08:20
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Re: Won't Start on First Try, Will on Second

i did some digging around, the valve I'm referring to is called a rollover valve, that might help you source a replacement easier.
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  #15  
Old May 7th, 2012, 08:49
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Re: Won't Start on First Try, Will on Second

The rollover valve cannot be serviced. If it fails, the gas tank needs to be replaced.

I'd use the troubleshooting information I posted in post #2 to help isolate this. The failure of the check valve(s) on the fuel pump assembly is VERY common.
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