Made a trip to the hardware store yesterday. When I came out, the truck would crank just fine, but wouldn't start (98 4.0L 4x4). Tried adding gas, no luck. I had actually called a wrecker, but it eventually started after sitting for about an hour. All I did differently was hit the gas pedal a couple of times. Thinking it may be a low fuel pressure problem, I took it to autozone this morning (started it about 4 times now with no problems). Checked the fuel pressure, and it sat at a solid 65 lbs at idle. I tried holding the throttle open and it stayed at the same pressure. I forgot to try with the vacuum off.

First off, I've seen some people say 60 lbs is right, but more say it should be at about 45lbs. 45 seems right since the fuel return is on the block, not on the pump. I'm guessing the fuel damper went out, but is there any good way to check it? Also, since the damper is vacuum controlled, would a bad vacuum cause this problem? Third, could high fuel pressure cause it to not start? That's the one I'm most worried about since I have no idea what was wrong there.

 

1998+ Rangers utilize what is called a "mechanical returnless" fuel system. These returnless fuel systems have the following characteristics:

(1) there is no return line running back to the fuel tank from the fuel rail;

(2) designed to operate at higher fuel pressure - 64psi (+/-8psi);

(3) the fuel pressure regulator and check valve are now located in the fuel tank with the pump assembly, not on the fuel rail.


So then, 65psi fuel pressure is spot-on for your '98. It shouldn't deviate from that number all that much, even at different RPMS.

Did Autozone test for fuel pressure leakdown? You should verify that fuel pressure remains within 5 psi of the operating fuel pressure for 1 minute after the fuel pump is turned off.

The fuel rail "pulse damper", located on the fuel rail, reduces fuel system noise caused by the pulsing of the fuel injectors. It has nothing to do with controlling fuel pressure. The vacuum port located on the damper is connected to manifold vacuum to avoid fuel spillage in the event the pulse damper diaphragm were to rupture. As such, vacuum does not control the damper in the sense that you infer. I don't know of a test for the damper itself, or whether a bad damper can cause a "no start" condition.

If it happens again, keep in mind that pushing the throttle pedal to the floor (WOT) during cranking (and holding it there) will cut off fuel to the injectors. This could help to determine if you are looking at a "flooded" condition.

 

Kinda sounds like a heat soak vapor lock problem. Was the fuel level well below 1/4 remaining & was it unusually warm when the no start happened.
Did you just fill up from a different, no name brand station, or out of the way low volume gas station, where the vapor pressure may not be seasonally adjusted, or be out of spec because of low volume sales????

 

I didn't check if it held pressure after the engine was shut off. It took long enough to find a working pressure gauge. I can take it back and check it again later this evening. There was a valve on the gauge to drop the pressure. It would come right back up to 65 lbs when I dropped it to 0. As for gas quality, it had more than half a tank I think. The gauge read 1/2 a tank, but it is a ford gauge. The last time it was filled, it would have been at a name brand location. However, I'm a student, and it has been a few weeks since it had gas. We did add some fresh gas to it, but that didn't seem to help. It was a hot day (~100 F), and it was sitting in an open asphalt parking lot. Not sure what the vapor lock problem is?

 

What was the level of fuel in your tank?
I've had hot no start issue with my 2001 4.0L manual trans. whenever the fuel was below 1/4 tank.
Got a new fuel pump installed today.
I got the old one home and put 12v to it and it was locked up tight.
Tapped it a couple of times and that broke it free,
Now I've got a spare fuel pump,

 

So, you have fuel pressure and still no start? I would check for either the injectors not firing or the ignition not firing. To check for spark, hook up a timing light and see if the light goes off when you crank the engine.

I've read in my shop manual that the camshaft position sensor is used to determine when to fire the injectors. And I've read other posts where people have a no-start due to a bad crank position sensor. I would suspect either one, leaning more towards the crank sensor based on what I've read on various forums. I don't know for sure that the camshaft position sensor is used exclusively for fuel injector timing and that the crankshaft position sensor is used exclusively for ignition timing. But, the crankshaft position sensor is shown on the ignition schematic while the camshaft position sensor is shown on the engine controls schematic.

 

I don't know for sure. I would guess it had over half a tank in it since it usually has between 1/8 and a half when it reads empty. I haven't gotten to fill it up yet. My parents had it for a couple of weeks and I haven't put any in since, so I don't know how long its been since its last fill up. My friend brought a 6 gallon can and added that much to it. It still wouldn't start right away. It sat for about 40 min after that before it started.

 

I forgot to mention that you can check the crankshaft position sensor with a DMM. Check for a short or open circuit when you're experiencing the no-start.

It sounds like you have the issue when the engine is hot. If you experience the problem at home, you could blow compressed air on the crankshaft position sensor to cool it down or some of that electronic parts cooler and see if it helps.

 

It did it again today, and it wasn't nearly as hot. Maybe 86 degrees. I haven't driven it in 5 days, so nothing should have been warm. I also got a fuel pressure gauge in the mail, so I put it on there and had a friend read it out. It was at 0psi when we started. I kept turning the key on and off to run the pump, and it slowly built up pressure. We couldn't get it to pressurize above ~48 pounds. However, once it got there, it started and the pressure came up to 65ish no problem. I let it idle for a little while and shut if off. Checking the gauge a few minutes later, it had dropped to around 61 lbs. I expect it to drop some without the pump running. I also assume it took a while to build up pressure with the gauge on there because it needed to fill the rubber gauge hose. Does this sound correct? Also, is there anything else I should check? I'm assuming now its not a heat issue.

 

I'd say you are probably looking at a bad fuel pump.

A good pump should pressurize the system on the first twist of the key. It shouldn't take several "primes" to get it up close to specs. The gauge being attached is a non-factor.

Has the fuel filter ever been changed? It would be worth your while to change it prior to replacing the pump.

 

Got a new fuel pump in it. It didn't realize how much power was missing. It still starting hard, but its always done that. Anyway, it will be getting a new fuel filter. I'm guessing it never had one. We bought it used 2 years ago, so I don't know for sure. I would have put one in already, but all 3 quick disconnect fittings are stuck in place. Anyway, would anyone know where I can get a new fuel fill relief hose? I found a new neck hose (the 1.5" one), but I can't find 3/4" hose for the relief one anywhere. I've checked locally and on line. Thanks for the help

 

Spoke too soon. It has a new pump, but it's doing the same thing again today. Cranks, won't start. On a whim, I opened the fusebox under the hood and felt them all (the Electrical Engineer in me says look for something not right), and oddly enough, I found something. Relay 4 (PCM Power Relay) is getting a lot warmer than the rest, to the point it hurts a little to touch it. The key is also warmer than normal, but that might just be a result of being put into a warm ignition. Either way, any more ideas? I'm starting to think its an electrical problem, but I'm not sure where to look. Still no codes.

 

Try swapping the hot #4 power relay for a like one not needed to run the engine, like the AC power relay & see how it goes. The under hood power relays are a known problem part & heat soaks are known to affect them. Could be worn, or corroded, high resistance contacts causing an under load voltage drop to the computer. Look in at the relay socket contacts, to make sure they aren't corroded, or loose fitting. Let us know how it goes.

 

Checked the bottom of the engine compartment fuse block. No loose connections, and no loose wires (wiggled them all, all nice and tight). Did the same with the header for the PCM. All tight and no corrosion in the header or the computer. Measured the resistance from the PCM side of the relay to ground. With the header off the PCM, it measured 3170 ohms. With the header on, it was 433 ohms. The last number makes sense since I'm sure the PCM power has semi-conductors in the path. Anyway, but it all back together, and the thing started easier than it ever has. I'm really thinking a wire somewhere is loose now, and all the wiggling knocked it back into place for now. I guess I'll wait until it does it again and just start wiggling until it works. Then I'll know where to look. Also, the relay is no longer hot.

 

OK, good trouble shooting & feedback. Check voltage drop on the battery to body & engine ground points. Try a wiggle test with the engine running.