Renix fuel pressure question

[BrettM]

I searched a little, and I'll go do some more... but first:

I have a no-start issue with my '88 4.0, and I'm pretty sure it's a fuel issue. When I put the key in the ON position I can clearly hear the fuel pump click on for a few seconds. When I depress the schrader valve on the fuel rail to check pressure, it gives a tiny spurt, about 3 inches for less than 1/2 second, then nothing. If I press it again, nothing. If I turn it off then back on I can get another little spurt out of it.

Question; shouldn't it maintain pressure?

So if I am correct that I have a fuel issue... I replaced the fuel filter a few weeks ago, I can clearly hear the fuel pump working, I already bypassed the ballast resistor.

Question; what else is involved in the fuel system?

[old_man]

The fuel pump only runs for a few seconds to build up pressure. It then stops until you start cranking.

My feeling is that it is not a fuel issue. Just because the one way valve dies, does not keep it from starting. It only makes it take a few seconds longer. You said you got a spirt of gas. That should be enough to at least get it to sputter and try to start.

Explain your complete situation along with engine specifics and I can help you. When did it start? Can you get it started at all? Do you have spark? Does it fire at all?

[BrettM]

It sputtered and stalled last night like it was out of gas (I have over half tank) and not it tries to start and will sputter heavily for a second or two after I stop cranking the starter.

I actually haven't checked for spark because I haven't had anyone with me to help (and no remote starter). That's next, but with the way it sputters it sure seems like fuel.

[old_man]

If you can get someone to crank it for you, there is a simple way to check if it is fuel starvation or not. Pull the hose off of the trottle body. While it is cranking, squirt some carb cleaner down the throttle body. If it fires, you have a fuel starvation problem. If not, the problem is elsewhere.

[BrettM]

update;

has spark. starter fluid down the TB doesn't help. the squirt out of the Schrader valve is present, but very unconvincing.

an engine needs air (in and out), fuel, and spark. it's getting air in, if the cat was plugged it would at least run for a few seconds (right?), there is at least some fuel at the rail and I sprayed starter fluid in the TB, it has spark.... sooo... WTF? could it be the cam position sensor? is that at all likely?

[old_man]

OK, a common problem with working on no start engines is that they get flooded. For some reason, XJ's do not like to fire if the plugs have gotten wet with gas. Pull the plugs and wash them with starting fluid and let them dry completely before putting them back in. Baking them in an oven is not a bad idea. Personally i throw them in the glass beader cabinet and clean them up but thats not something everybody has laying around. I use the cheapest Champion plugs I can get, so spend $6 and get a new set of plugs.

Before reinstalling them, hold the tps all the way in the open position, as well as holding down the accellerator and crank the engine for 20-30 seconds to dry out the cylinders. Holding the tps all the way open, tells the computer that the engine was flooded, and it shuts down the injectors.

Once that is done, you can try starting it. Don't touch the accellerator.

Good luck.

[BrettM]

That doesn't explain why it stalled in the first place, and when I pulled one plug to check for spark it didn't seem wet at all. It also sat over-night, wouldn't that clear it up if it was flooded? ... I'll try some new plugs though, just in case...

If the CPS, MAP, or other sensors were failing, I wouldn't have spark at all, correct?

[GSequoia]

Brett,

So when you hit the valve does air come out too? Sounds a lot like a blown fuel line in the tank (has happened to me a couple times). To fix this you gotta pull the pump / sending unit and replace the hose that goes between the fuel pump motor and the outlet tube.

[BrettM]

Brett,

So when you hit the valve does air come out too? Sounds a lot like a blown fuel line in the tank (has happened to me a couple times). To fix this you gotta pull the pump / sending unit and replace the hose that goes between the fuel pump motor and the outlet tube.
good question...

[old_man]

If he was fuel starved, it should have fired up when he used starting fluid.

[GSequoia]

Oh, I thought he said that starter fluid did make it boom.

[BrettM]

well I don't mind spending $10 on new plugs, so I'll be back in about 1/2 hour to let you know how it went...

[BrettM]

$11 for some Champion plugs and everything works great. Good call old_man... but I'm still confused why it died in the first place...