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Hot start issue

X

XJeeper87

NAXJA Forum User
Location
FL
After running around for awhile when I try to start my XJ it will turn over and pop and sputter as long as im turning the key as soon as I let off it dies. If I keep the gas pedal half way down it will eveuntally start. But if I dont rev it up untill it clears out it will stall or run Horibly. once its running and I clear it up its FINE runs perfect.

BTW its a 87 4.0L Renix new TPS new oxygen sensor

Any ideas as to whats going on?? Im leaning towards the injectors. They have 280,000 miles on them probably time to replace them with some 5.0L ones :)
 
Those dont seem like the problem cus it runs rough till I rev it up. time doesnt fix the rought running problem just running fuel threw it
 
1. Test fuel pressure with a fuel pressure gauge at the fuel rail. Target is 31 psi at idle and 39 psi with the fuel pressure regulator disconnected

2. Did you replace the TPS because of this problem? Did you adjust your new TPS? Your vintage is adjustable and adjustment is important. You'll need a meter and a manual or check out below link for some information on this.

3. How fresh is your tuneup hardware? Plugs, wires, cap, rotor? Gotta have a good ignition system for quick starts.

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm
 
I tried pressurising the fuel rail by cycling the key 3 or 4 times no change. When it finally starts it sounds like an old carbed vehicle. Instead of like a fuel injected one. instead of purring it is like pop pop pop pop pop
 
Gotta have hard fuel pressure numbers with a gauge. A gauge can tell you first if you have the proper pressure for a clean start, if you have sustaining pressure, and also can help you with tracking a leakdown problem (leaky injectors, etc).
 
Well I have hot start probelms with it only sitting for 10 minutes I was out riding stopped to take a leak got back in and it didnt wanna start so I dont think that is enough time for the fuel to leak out. Im not saying I dont need to check fuel pressure just stating that.
 
Test the fuel pressure and do the leakdown timing test.

Sounds like your injectors might be leaking, pooling fuel in the intake manifold--will run like crap when you get it started until the excess fuel is gone.
 
i have a 2000 xj that does the same exact thing and from what i got out of it is a hot soak running around town then shutting of the enging when it sites for a few the gas in the injectores get vaperized and couses and air lock try and get it real hot the when u shut it off open the hood see if it works just what i do but like i said mines a 2000 and i havent found a way to fix it yet good luck let me know how u do.
 
and u dont have a fuel rail so itas probly not the same thing but thought id put it out there
 
rjm7263 said:
and u dont have a fuel rail so itas probly not the same thing but thought id put it out there
Click to expand...

OP, call the police, you have been robbed! :D
 
My '87 renix had this same issue. I replaced and checked tons of things. It ended up being a failed heater circuit in my 02 sensor. i was convinced I had heat soak etc. Try a new 02 sensor at some point.. or at least ohm out the heater circuit in the 02 sensor and see if it reads open.. actually I'd just replace it either way.
 
02 sensor is BRAND NEW not even 2 weeks old and this jeep has had this issue as long as ive had it. its not even a big deal just wondering if it is a cheap fix
 
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