br1anstorm
NAXJA Forum User
- Location
- United Kingdom
My 1993 XJ 4.0 (auto, injection, US-spec) - with 106,000 mostly on-road miles - has developed an occasional starting problem. I've searched the forum (and FAQs) and there seem to be so many possible causes I need help in narrowing it down.
First off, I haven't done any recent work on the engine except to fit a new Optima battery when my 5 year old AC Delco finally died. But the starting problem had showed up before that, and it has now recurred.
Symptom is that the starter motor cranks, the engine turns but doesn't fire. After 2 or 3 attempts, if you floor the gas pedal and try again, it starts. Once running, everything is fine (no rough idle, no stalling). The starting problem first showed a couple of months ago, just after filling up a near-empty fuel tank. Sometimes starting was normal; sometimes it wasn't. Battery and spark were OK - it simply felt as if fuel wasn't getting through - thouh I guess it might also mean it was flooded? Typically, when I took it to a workshop, I couldn't show them the problem - it started faultlessly every time!
Then the problem seemed to go away. I assumed the cause might simply have been bad or dirty fuel (crud stirred up when filling the empty tank) or a temporary fuel blockage. After several more fillups and a squirt of injector-cleaner all has been well for a while.
Now the problem has reappeared. Just occasionally, it cranks but won't fire. Flooring the pedal (which I would normally never do...) when turning the key then seems to get it going.
I'm not keen to begin randomly dismantling/replacing parts on a guesswork basis. What is the most likely problem - is it fuel-supply related (pump, filter) or is it settings/sensors/controls (I'm not sure I understand all this TPS, IAC, CPS stuff)? What checks/tests should I do, and most important, in what order, to pin down the problem? Would there be any diagnostic codes, and how can I check them? (I'm in the UK, and local dealers don't have much expertise on a 14 year old US-spec XJ, so it's down to just me and the Haynes manual!)
Any advice would be welcome...
br1anstorm
First off, I haven't done any recent work on the engine except to fit a new Optima battery when my 5 year old AC Delco finally died. But the starting problem had showed up before that, and it has now recurred.
Symptom is that the starter motor cranks, the engine turns but doesn't fire. After 2 or 3 attempts, if you floor the gas pedal and try again, it starts. Once running, everything is fine (no rough idle, no stalling). The starting problem first showed a couple of months ago, just after filling up a near-empty fuel tank. Sometimes starting was normal; sometimes it wasn't. Battery and spark were OK - it simply felt as if fuel wasn't getting through - thouh I guess it might also mean it was flooded? Typically, when I took it to a workshop, I couldn't show them the problem - it started faultlessly every time!
Then the problem seemed to go away. I assumed the cause might simply have been bad or dirty fuel (crud stirred up when filling the empty tank) or a temporary fuel blockage. After several more fillups and a squirt of injector-cleaner all has been well for a while.
Now the problem has reappeared. Just occasionally, it cranks but won't fire. Flooring the pedal (which I would normally never do...) when turning the key then seems to get it going.
I'm not keen to begin randomly dismantling/replacing parts on a guesswork basis. What is the most likely problem - is it fuel-supply related (pump, filter) or is it settings/sensors/controls (I'm not sure I understand all this TPS, IAC, CPS stuff)? What checks/tests should I do, and most important, in what order, to pin down the problem? Would there be any diagnostic codes, and how can I check them? (I'm in the UK, and local dealers don't have much expertise on a 14 year old US-spec XJ, so it's down to just me and the Haynes manual!)
Any advice would be welcome...
br1anstorm