XJ6 VDP 1987 Won't start

XJ
22

Yes.

Leaking is one failure mode. Inability to control fuel pressure is another. Lack of leaks does not prove the regulator is controlling pressure correctly.

It can

Cheers
DD

1 Like
23

I replaced the fuel pressure regulator and plug wires. Still a bit rough so I took out the injectors and used a Gumout cleaning tool to back flush them. I found one that was clogged. Test sprays are a single direct stream. Is that correct or should it be a spray cone pattern?

24

Pattern should indeed be conical, Kim - a fine mistā€¦

While the amount of fuel may be correct, the single stream means large droplets - which interferes with the combustion processā€¦

Frank
xj6 85 Sov Europe (UK/NZ)

25

I bought an ultrasonic cleaner and did the injectors. Two seem to have died electrically and the others have various spray patterns. One has a straight stream which I think is the older version of injection - spraying at the back of the intake valve. I need to buy a new set. Which ones are compatible for this?

26

Calling @SD_Faircloth

27

The spray patterns should be equal, Kim - conic and misty - obviously the cleaning was not successfulā€¦

Electrically, the resistance between the two prongs should be 2,4 ohms, indicated the coil is OK - short or infinite means replacement. Likewise, grounding each prong to injector body should read ā€˜infiniteā€™ - otherwise; replaceā€¦

If injectors pass the electric test but fail to provide the proper spray pattern; a more thorough cleaning may revive them - they may just be stuck/clogged

Whether replacement, or professional cleaning, is best solution is arguableā€¦

Frank
xj6 85 Sov Europe (UK/NZ)

28

There is only one that works. 0280150153 Bosch. No longer in productionā€¦ Everything you see will be rebuildā€¦by someone. These injectors have a pintle. The pintle does not create a conical spray patternā€¦similar to an upside down ice-cream cone shape /\
These will typically have what I refer to as a pencil sprayā€¦a straight down, non-fanned out spray. STRAIGHTā€¦like a pencil. The coils on these old Bosch injectors are really very very good. They almost never fail. It is possible you overheated the coils during your testing. On these old engines, these remanufactured injectors may sit at a warehouse for months prior to being sold, pulled out and mailed without further thought of whether it still operates. Word of caution. SD Faircloth

29

Indeed, Faircloth - testing with 12V the current will be some 5A - high enough to burn out the coils unless applied very briefly. The operating current is in the 1,5A region - and the injectors are then cooled by fuelā€¦

Frank
xj6 85 Sov Europe (UK/NZ)

30

I replaced the injectors with the correct type, reconditioned and flow matched. Still tough starting. I bought a new AFM and installed it and it fired up immediately. I have the air bleed open about 5 turns. It idles in Park at about 1100-1200 but when I put it in gear and the RPM falls to around 800 it dies.

31

I presume this is with the engine cold, Kimā€¦?

The bypass is used for fine tuning the mixture - due to the limited range it has little effect on the engine behavior - particularly with the engine cold. The ā€˜normalā€™ bypass is around 2 turns - and you may try that to slightly fatten the mixtureā€¦

However, closely watch the tacho as the engine quits; it should show rpms while the engine winds down. If the tacho drops to ā€˜0ā€™ while the engine is still turning; ignition has failed - causing the engine to quit.

This are just preliminaries - itā€™s a bit odd that changing the AFM should improve starting, but bring on other symptoms as described. What else did you do to rectify the hard startingā€¦?

Frank
xj6 85 Sov Europe (UK/NZ)

32

Wow, I am learning soo much,thanks for all this advice
My xj6 has the same issues ā€¦and is also an '87 but has an '86 power trainā€¦did not change the electronics mounted on the carā€¦
Anywayā€¦thanks
Mitch

33

Hi look at the AB14 amp fire unit ā€¦ I did a forum up on my page about that ā€¦ Iā€™d say myself thatā€™s your problemā€¦

34

Also relatedā€¦

35

Parts replaced:
New AFM.
New distributor pickup module.
New cap, rotor, wires, and plugs.
Reconditioned flow matched injectors.
New fuel pressure regulator.
Faily new fuel pump.
Fuel pressure is good and injectors flow freely as tested by energizing with pressure drop.
Noids verify injector harness good.
Good spark at plugs.
18" vacuum at idle, no leaks.
Compression test cold 125-130 psi all cylinders.
2 turns out on the AFM adjuster seems to run best.
Mechanic advance in distributor turns freely and no leak in vacuum advance capsule.

My final issue seems to be that it will not idle below about 900rpm. It just suddenly dies below that although the timing light still flashed on the way down. It idles fine at 1000-1100. I did my best to determine that the zero advance mark on the damper was TDC on #1 cylinder. When set to 17 degrees at 1000 rpm, it wonā€™t start and kind of chugs/runs barely at the speed of the starter. When I advance the distributor it will suddenly pick up and run normally and will allow retarding back to spec and runs fine. The advance it will start at is 40 degrees BTDC at 1100 rpm.

On another note, when replacing the starter, I discovered that the trans vent pipe was not in the case and it was spitting out fluid while running. I reseated it and tie wrapped it to hold it in place. How is this pipe normally retained?

36

Is all this with the engine fully warmed up, Kimā€¦?

All running adjustments, idle etc, must be made with the engine warm. Three more questions; what is vacuum reading on the dist vacuum hose, have you checked the CTS - double checked ignition sequence?

I suspect a fuel/air issue, the advance reaction being a blind - but given the wholesale change of parts; there might be something thereā€¦

Frank
xj6 85 Sov Europe (UK/NZ)

37

All was done with engine at 90Ā°C. No vacuum at distributor at idle but there is off idle. CTS checked awhile ago. The resistance value matched the ambient temperature at the time. EAV works OK, runs a couple of hundred rpms fast and drops in about 3 minutes. I disconnected the hose to the throttle body and plugged it and there was no change as in extra air still entering.

I have a timing device which lets you screw it into the plug hole and turn the engine manually both ways to a stop say 20 degrees both directions to check the timing marks. I canā€™t find a way to turn the engine over by hand even with the plugs out. Any suggestions on this?

38

I am not adding much. kinda of like shots in the dark.

  1. . Somethong s wrng in te timing behaviour. I can not put my finger on it. Is there not a bolt head on the cmpener that you can put a socket on/ Is there not a dust cover on the bottom of the trnsmssin, to access theteeth on the flex plate .to bar the engine over/ Hs the outter part of the damper slipped, making ghe timing mpoaaaible to set correctly.\If you can find a way to bar the engineover, or use a remote crank and the eigntion off, Place a wooden rod in #1 cylinder. %1 o these engies is the one by the firewaol. opposite of most other 6 cylinder enges

  2. does your engine call for ported vacum take off or manifold/

  3. You have a vacum leak somewhere.

4.A leak in he flex duct?

A lot to digest, huh>

Oh, 40 degrees is alot of advance??

Oh, sticky vac advance in he distributor? Same for the mechanial, stiky

My typing is worse thn ever. got an eye injection yesterday, ug. Left eye still a bi fuzzy.

CHJ

2 Likes
39

Carl,

donā€™t worry about your typing! Even with troubled eyesight and resulting typos your posts are still most valuable and helpful!

Best wishes for your eyes!

Jochen

75 XJ6L 4.2 auto (UK spec)

1 Like
40

Which means you have ā€˜portedā€™ vacuum, Kim - and 17 degrees advance is in the ballpark for this set-up.

That you read 18" Hg idling actually indicates an engine in good condition - that it will not idle below 900 rpms is difficult to understand. Likewise; that timing light still flashes during engine wind-down implies that ignition does not cause the shut-down.

A double check is to watch the tacho - it should read engine rpms untill the engine cease to turn. Also, the timing light, between coil ā€˜-ā€™ and ground, will interfere with ignition voltage and spark energy - it should only be used as an initial testā€¦

As you have changed the dist pick-up coil
(why): did you carefully check the air gap ( 0,008 - 0,014") and parallel to the reluctor teeth? Mis-set it may interfere with ign amp function at low rpmsā€¦ .

Also; check that the throttle gap is set to spec, 0,002" - and that the throttle body is clean.

You should certainly reverify ignition sequence - crossed plug wires will interfere with engines ability to run at low rpms. At higher rpms the engine may run well enough on 4 cylindersā€¦

Further; you may have an air leak, engine running lean - and at low rpms may not have enough power to idle.

Donā€™t know that device; the normal method is to use a micrometer to verify TDC at #6 cylinder. Such ā€˜mechanicalā€™ check, even without the precision of the micro is adequate for anything but a gross errorā€¦

In short, Iā€™m somewhat in the dark pending further tests as outlined. Itā€™s probably something simple - easily remedied once foundā€¦:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)

41

Thanks Jochen!

Added to clumsy fingers!!!

Better today
eye meds have worn off.

CHJ