i had one of thoes gauges for a while lol, i had fuel taped to the windsheild oil pressure where the whindsheild wipers go and temperature taped to the rear view mirror

 

And if the the injectors aren't delivering enough fuel, what's the first the thing you're gonna check? Fuel pressure!

Basics, basics, basics! Ask ANY veteran tech, instructor, or field engineer....and I can promise they'll all tell you to start with the basics. Any checking fuel pressure is a fundamental step whenever a fuel delivery problem is suspected.


Cheers
DD

 

Good, then you know it can be done and there's nothin' stopping you :-)

Cheers
DD

 

Whenever I get a case the first thing I do is the basics. 75% of the time that is all is needed to find the problem. Th technicians all think I will arrive with some super secret info from the factory. But usually just a thorough logical check of the basics finds the problem.

 

Hmmm, i'm running into the same issue too with my '86. However, the shift point seems to be inconsistent. On occasion, it will rev out to 6k or so, but it's usually going to be 4200-4500 full throttle in D and i'm dying to get this rectified. I did the single coil conversion to no avail, and a local shop checked the fuel pressure recently which checked out. I'd love to check the AFR but i sold my lm1 a few years ago and i just hate buying things twice. Just like to see if others have had different issues lead to the same symptom first.

It's not sputtering or anything, or seeming to cut out. Just seems like a shift that's way too early to me. Could it be the vacuum modulator perhaps? Does the fact that it does sometimes rev out point to any factors? Thanks for any thoughts.

 

I went manual because i like to run the whole power curve from 3200-5900ish then slam to 3rd and repeat. Ill check tomorrow and report back!

 

when it cuts out does it sound like an asmatic after a 100mnew dash? Cus thats what mine does

 

Not quite sure of what your describing but I don't think it's the same issue.

Maybe you should start a new thread with "Shifts too soon at full throttle"

Cheers
DD

 

that sounds like vacuum or kickdown to me

 

when were maxing out stock injectors by running smaller pulleys, bigger cams, intercoolers, turbos, improper tune or other issues etc. we see a big drop in fuel pressure?

no, we see a crap ton of KR and a super lean AFR.

 

Big difference between calvin's stock fuel injection issue and the boy racer, bolt on go fast parts. Let's not get him confused with too small injectors, etc. His problem is something is not working as designed and by being systematic and thorough he will solve his problem.

3 things to look at:

1. Ignition- can it produce a spark at high RPM? dual coils can if both coils are working. Now if you replaced either of these coils did you use the correct resistance primary? Did you epoxy the secondary tower on the second coil? Or did you replace the coils with one? If so then is the replacement one up to the task?

2. Fuel- Fuel pressure AT the time the concern appears needs to be measured. Just because you have pressure at idle does not mean you have good pressure at high RPM. You could have a volume issue. Bad pump, restriction in the system can cause it to drop. Some people have reported a crush fuel line under the car which can reduce volume available. Also do not overlook the fuel filter or the line from the main tank to the sump tank. In the sump tank there is a mesh filter on the pick up. Those can get plugged with rust and other garbage.

3. Air- In or out. If you have modified the air boxes or something take a close look at those. Usually the mod is to make them less restrictive but you can always remove the air filter and go for a test run. An engine has to breathe to work properly. If you still have the stock system you may have a cat converter that has melted and partially blocked the exhaust. This will cause lack of power and less of an ability to rev up. Unfortunately they are not easy to remove to check but non-the-less they can't be ruled out. The assumption is made that your engine is in good condition.


Make a list on paper of all the possibilities. Do not rule anything out. Now go through your list and check all the easy ones right away to eliminate them. Then work your way down the list from easy to hardest. You will fix it.

 

What's "KR" ?

Anyhow, there are many ways to skin a cat and no doubt that wide band O2 sensors can reveal many things. IMHO they're of most value when tuning a modified engine, as you describe.

Calvin can decide if purchasing and installing wideband sensors is the optimal method trouble-shooting the fuel and/or ignition problem on his (apparently?) stock engine. My gut feeling is that, if he goes that route, he won't be one bit further along in diagnosing his problem and he will have spent the money needlessly.

Here's a couple wild thoughts from wayyyy out in left field.....

If elects not to go with wideband sensors, knowing that they're not a *requirement* for a good diagnosis, the money saved can be put towards the acual repair of the car.

Or perhaps the savings could be put towards the purchase of a small set of noid lights, a fuel pressure gauge, a DIY-quality DVOM, and/or other tools that will prove useful not only the the XJS but other cars as well.

Or, (getting really crazy now!) maybe even buy a full set of manuals for the XJS...something that so many people seemingly refuse to do even though they're available for only $30 or so on CD/DVD.

Cheers
DD

 

is there any way to check coils while running?

 

Yes with a scope.

 

Doug,

Stop being so crazy! Buy tools and manuals? Pretty soon you will suggest actually diagnosing rather than just changing random parts. You really need to get some sleep.

 

elaborate
please

 

Greg is talking about an oscilloscope it displays the wave form of the coil.

What coil/s are you running?

A coil is a trasnsformer if the primary and secondary dc resistance is ok the chances are the coils are good. Check the resistance with a meter.

 

It was the coils, i switched to two msd super capacity coils and that fixed the problem revs to 6500 in gear now

 

i'm having problems with my rpm

 

I have a 1989 Jaguar XJS. My car rpm keeps going up and down. How can I fix this problem?