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Hesitation Hard Starting

XJ Un-Limited

NAXJA Forum User
Location
Mesa, AZ
My 92 XJ just started doing this recently. Hard starting (takes 2+ trys for longer duration than normal) no matter what the engine temperture is. The hesitation is under acceleration, once at speed, it's just fine.

I checked out the vacuum lines to make sure they're ok. I did the key technique fault check (no OBD I scanner) and the readout came back code 13: MAP Sensor, No change in Manifold Absolute Pressure (MAP) between engine off and on. Check circuit and MAP sensor.

So I replaced the MAP sensor, but the XJ still runs like doo-doo. I re-ran the codes, came up with a 12 - battery disconnected. So now I'm a little more stumped. Seems like none of the auto stores have OBD I capabilities anymore.
confused.gif
Any ideas???
 
None of the auto parts stores ever had OBDI capability, as every manufacturer required different adapters and software. When OBDII became universal and generic scan tools became cheaply available, AutoZone and others jumped on the bandwagon and offered the service for free.

Leave the key on for 10-20 seconds before you try to crank the engine. See if it starts faster then...it might have a fuel pressure problem. Get a guage on the rail and check it.

As for the hesitation, when's the last time you replaced the plugs/wires/cap/rotor?
 
Bought and hooked up a fuel pressure gauge today and here are the results. When keyed on, NO pressure (zero, nada, zilch), you can still here the pump prime up though. Once it finally started, it got no higher than 20 psi. When turned off, fell immediately to zero. So, new fuel pump, here I come.
 
I had a 92 that always took like 8 seconds of cranking to start. It was like that for years. I believe the fuel was bleeding back into the tank when the ignition was off. I changed the pump and it was all better. On the bright side, you can change the pump without dropping the gas tank.
 
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