Give it a try, the worst that can happen is the tank and the gasoline in it will detonate with enough force to destroy the known universe....
Seriously, remove the gas cap and blow back VERY gently, you should hear bubbling in the tank, don't use a compressor, just blow into it, compressed air might possibly damage the filter and/or pump.
It sure sounds like fuel starvation but it may not be?
All such problems became nothing more than a bad memory when I moved from Seattle to Colorado. I feel your pain. Heh, heh.
Cheers,
Earle
You could be real slick about it and use regulated air to about 1 PSI or even blow on it (as you can mkae about 1 PSI or so that way) and it should blow easily. If not there is a restriction
There could be a vacum leak in feed line that cause air to be drawn into fuel line at higher flow rates which then causes pump to cavitate and loose pressure.
----------------- TheSnoMan.com
Still no joy.
Have a fast idle (2000 rpm) issue when first started that mellows down.
It seems to be an RPM limiter under load.
If floored in neutral, the engine will die, it will not catch back as the rpm comes down unless the pedal is let up on.
If coaxed up in neutral the engine will rev high.
When in 1st, it picks up fast to about 2000 rpm, then hits a wall. Holding it to the floor causes 'misses' and sputtering with a decrease in power and speed until the pedal is let up on.
I have no way to verify fuel pressure other than to say this power issue has been going on for several weeks with a 'stable' screw up. When pumps go, they usually go sooner than later totally, but....
Things done:
Cap and rotor
Gas filter
Air filter new
Ran with open gas cap
Checked plugs, all 'very' even and evenly burned almost to the 'worn out' point with a perfectly 'normal' coloring. Gap was almost 50, put it back to 35.
That would go with the plug wires also checking out ok on my meter with an ohm check. They are OEM 'lifetime' wires about 10 years old. Checked and cleaned CPS (about 5 years old) with attention to the wire's routing.
Cleaned main battery terminals and cable ends.
Cleaned TPS and checked it for smooth ohm reading all the way up.
Cleaned IAC connection, but not the unit itself??? Can that affect top end?
Cleaned coil connections and verified the meter readings. Seem ok. Got
1.5 ohm between the plus and minus pins, infinity between plus and case and 'less than infinate' my books says between coil negative and high tension post or 4.5 K ohm on the meter.Unplugged EGR. No change so put it back.
Cleaned connections on the MAP sensor and verified the vacuum line.
I have to wait until later to have a friend go under to blow out the fuel pump.
Mike
Mike Roma> Ok, I am on a fishing expedition for likely things to check.
The anti drain back check valve in the pump will make it difficult, if not impossible to blow back through the pump. However, if it's easy to blow back through it would indicate the the rubber hose from the pump to the sending unit outlet has come loose or failed. Very common and most likely cause of the problem you describe.
You could also be describing an ignition coil failure. Even if your measurements look good, and it appears to create a strong spark, it could still be shorted internally, causing your problem under load. You'd need a scope to see it though.
"L.W. (Bill) Hughes III" wrote
With a TPS and IAC?
Nice try, thanks.
The pump holds blow back pressure.
It didn't have any pressure when the filter was unhooked though....
If the spark was messed, I would think I would see dirty plugs, not perfect wear ones....
Do you or does anyone know if there a return line pressure valve on this
88 4.0 or is it just a metered hole?I am thinking about pinching off the return line to see what happens....
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06
Not necessarily.
The fuel pressure regulator is on the fuel rail at the front. It's a spring loaded diaphragm with a vacuum hose attached to it. Spring pressure determines fuel pressure. Vacuum assists in overcoming spring pressure to open the bypass under low load (high vacuum) conditions. On high load (low vacuum) it takes more fuel pressure to open the bypass. The result is slightly higher fuel pressure under load.
Be careful pinching off the return line. You could easily end up blowing off the hose I mentioned earlier.
You really need a fuel pressure gauge to see what's going on. An old low side R12 gauge would work. Otherwise you're in for some guesswork.
Mike, a $15 fuel pressure guage set would have already saved you that much in irritation! A borrowed freebie would have been even better. I have the MPI manual for the Renix setup (87-90 or so) and it give a cookbook sequence that is pretty sure to identify about any fuel delivery problem. If it weren't for the bleed down check (how much it drops in 20 minutes) you could be done in 15 minutes.
Be VERY careful pinching off that return line w/o a guage! Even with a failing pump it would hit over 90 PSI inside a few seconds and that will definitely blow hoses, especially as old as ours are. The second is that the return line comes off the front end of the fuel rail and it's a metal pipe until it gets way down into the works - hard to reach and control - plus it is very likely old and ready to crack as soon as you pinch it. If you do this, pinch the line, have someone turn the key on and be ready to quickly turn it off. You really do need to scrounge up a guage. Until I found what I wanted, I cobbled one out of a cheap 0-100 PSI water guage I had laying around.
Mike, curious; what is the latest?
The vehicle hasn't been here, it is used by my wife to go to work.
I might look more at it this weekend depending on rain.
There is one ratty coil to ignition module connection I want to address and I want the fuel pump connection cleaned just in case.
Mike
We solved our power loss problem.
RIP
88 Cherokee 316K kmWe had a nice ten years together.
Don't even think there is enough metal left on it to make a new car door once it's melted down....
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 Canadian Off Road Trips Photos: Non members can still view! Jan/06Mike, Did you find out what it was ?
Dave Milne, Scotland
Nope.
Mike
Dave Milne wrote:
You getting another ?
Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ
I had another one with almost no rust to transplant the drivetrain over to but was unable to do so before the government showed up with a warrant to steal my second XJ for 'disuse'. I was not physically able to do the swap in time to prevent this theft so I had to sell it to a scrap yard.
My wife found a mint one owner 90 Cutlass from a friend with about everything new including BFG tires for $100.00 so we bought that. It goes on the road today and the plates come off the poor old Cherokee.
Mike
Dave Milne wrote:
Hi Mike,
Sorry to be thick, but how on earth can the government take your car for 'disuse' ? How long can you 'disuse' it before they decide that they have a right to meddle in your affairs ?
Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ
The second it has no valid plate and/or insurance on it, it is against the law to have it on your property here in Toronto Canada.
They also can come and steal the contents of your garage legally if the door is open or broken open. It is then consider 'public access' or some such stupidity. Because we rent they do not legally have to give us any warning to do this before 6 apes show up in a truck. I literally had to stand there with a large pipe in my hands while the cops came to shut them down long enough for us to board up the door. They were going to steal all my camping gear, my canoes, my tools, our bicycles, etc.
The cops were just a little sympathetic making the guy swear he wasn't coming back.
I had tow truck driver friends hear the police radio call and show up for 'moral' support too. heh heh...
I can't wait to get out of this hell hole, I'll tell ya.
Mike
Dave Milne wrote:
Pshh. Canada.
Get a big, slobbering Rottweiler ... or a gun.
Craig C.
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