dsmith

Thanks, you all have hit on my current thoughts. Keep it coming.

-I know what the readings should be, so not really a need to test another car. Couldn't hurt, but I don't have one!
-I agree on the vacuum leak and have ruled it out in my mind in general, but these cars being a bit odd, I'll leave it open for discussion.
-I'm also thinking fuel delivery/low volume, but how to check at load? I know the frequency valve can affect delivery volume, but what else can that I don't know about? Fuel pump is really a good/not good part, is it not? CIS should richen at WOT, but I'm leaning. What about the other air components? Could one be letting too much air past the sensor plate or something? I will check the volume flow at idle for a baseline.

The bad part about CIS is that 3 bad parts = PMO money these days, so I really want to be able to test any bad parts without swapping.

'til next week, gents.

wdonovan

Not a vac leak. Hard to check fuel delivery but pressure is a good indicator. Have a passenger watch a pressure gauge at WOT under load (must be driving). If delivery drops off, so does pressure because the injectors are requesting delivery. With those superlean numbers, I wouldn't waste time looking toward ignition problems right now. Dirty injectors can also cause a lean condition. BTW Is the exhaust system around the O-2 leak free? An air leak at say a header gasket can lower the O-2 reading on the meter without the engine actually running lean. If the closed loop O-2 sees this lean condition, it can compensate by fattening the mix although you swear you're seeing lean. Pull a plug after a WOT run?

dsmith

wdonovan, good ones.

-the exhaust has new gaskets and hardware, with on leaks. my 02 is unplugged and actually removed with the wideband in it's place, so let's rule these out for now.
-i do need to check pressures while driving. i just need to find an 8 ft long hose so i can run the guage to the interior. i don't have a provision for a passenger seat in my car. maybe my WUR is freaking out under acceleration??

so, next week i'll check:
-frequency valve per Bentley
-injector flow 1st time
-plugs again (hopefully not coated in aluminum)
-fuel pressure while driving 1st time, if i can find a hose
David

dsmith

Off my duff today and did a couple tests.

1. Monitor fuel pressure while driving. I duct taped the gauge to the rear window and bungied the lid to the bumper. I also put a thin piece of electrical tape on the gauge at 55psi to easily see if the needle went past it (going lean on control pressure under load).
-result: no change in fuel pressure (55psi), while the LM-1 was going lean. I held 3rd gear at 4k rpms and AFR was about 15:1. When I decel, I got some pops out the intake. So, I'm pretty sure System and Control pressure are not an issue under load. Any input on this?

2. Fuel delivery from supply line. Bentley states at least 1 liter of fuel in 30seconds. I had at least 2 liters. I used a 2 liter bottle and it filled before 30 seconds. So, I guess that means the pump is fine and delivery is good?

Baring an injector issue, i'm starting to lean toward an ignition issue.

Anything else I should check on fuel?
David

dsmith

A few more tests today, as I write here to myself...

1. Injector flow. I tested per Bentley and found all injectors to have a good pattern and strong, even flow. So, I'm done with fuel delivery and find no problems, past the initial slightly incorrect control pressures, AFAIK.

2. I pulled each spark plug one by one and replaced with the ones I removed prior. #1 I would call fouled. Pretty black with a dark insulator. The rest were slightly dark, but definitely not gray. 1-3 were darker than 4-6. Looking at the records and plug wires, I see that the left bank wires are older than the right bank. Hmmm.

I drove the car again and found it much better, with only some leaning up to 17:1 at WOT once past about 5k rpms. partial throttle and cruise look good for now. Still don't know why the fouling.

So, I'll order 2 sets of plugs (one for testing, one for when it's fixed), new wires and wire and plugs to replace the dizzy coax wire (it's brown with broken connector at dizzy), and clean the dizzy.

David

Welshy

Hi,

My SC showed the same symptoms and it was indeed the fuel pump which just felt tired - it sounded ok (although a little whiny) and pulled great at low and mid revs but plant the accel and the almost sounded as if it was missing and holding back.

Changed the pump ( £40 UKP and a few hours swearing and cursing underneath the car (again!!!)) and the problem was cured.

Didn't go as far as you have with reg supplies etc etc but I feel its a good place to start with those pesky troublesome SC fuel pumps.

Cheers

Wayne

dsmith

Thanks, Wayne. If it's that easy, i'll do it in a second!

Can anyone verify that warm control pressure does not change if the fuel pump has a problem at WOT? Mine does not change.

Thanks,
David

LaughaC

are you using a rotor rev-limiter? Mine malfuntioned once and the problem persisted through 2 other rotors before I realized the cap was bad too. Chased plug wires along the way until i remembered what a waste of time it is to rplace a rotor and not a cap and points. Maybe a new part you got is also bad?

dsmith

Yes on the rotor rev limiter. Though, again, would it cause lean running/intake backfires, etc? What is the failure mode if bad? 2 bad rotors and caps?

I just ordered plugs, , dizzy coax, and injector sleeves and orings (my sleeves are crumbling on the top edges). I'll try making my own wires first, if my connectors are good. I know it will end up being fairly simple, but damn the diagnostics already!

LaughaC

You're right. 2 caps & rotors should eliminate that. I hope it ends up as an inexpensive fix to offset all the hours you've spent chasing this gremlin.

wdonovan

If the fuel pump maintains pressure at RPMs, it's fine. That's its job and it's doing it. It means that in spite of higher fuel demand, it is supplying what the engine needs and has enough overhead to maintain pressure at the same time.

Mike Murphy

David,

"Wdonovan" is correct and I agree that the warm control pressure should be within spec as long as you as testing this using WOT in combination to high RPMS (not just revving at idle, which is a whole other topic).

I still think you have a fuel delivery problem, but I have some questions:

1.) Where are you taking the fuel pressure measurements from? Right at the output of the fuel pump?
2.) Is there anything between the point of your measurement and the fuel injectors?

Of course I know that the CIS system is probably there, but my point is "what else is there?" Fuel lines? Anything else? This might lead you to a possible blockage or some other component.

The reason why I think it's a fuel delivery problem is because when you lowered the output of the fuel pump back in post # 8 of this thread, you noticed that the problem got worse.

dsmith

Well, I was messing greatly with the mixture with no idea what the AFR actually was. I just figured it was lean, so I went rich to get the car through a 20 min race and back home (I didn't top 80mph). So, even though I got the fuel pressures set within range, the AFR was still way off, so it ran even worse. I figured that I at least needed to get the pressure right and the AFR right before continuing. I did that once I got the LM-1. Post #9 shows an initial reading at idle of 18:1.

The pressures are being read from CIS gauges attached between WUR and FD. It's my understanding that a blockage would have upwards of 100psi system pressure, correct? That and the fact that I have good fuel delivery from the supply line and good, even spray from the injectors leads me to believe no blockage. I'm learning on this stuff as I go, so don't be bashful if I'm down a wrong path. Just let me know how to test other possibilities.

Everything is fine revving at idle, so all my tests now are on the road pulls in 2nd and 3rd gears, with LM-1 and fuel pressure gauge attached.

I'm putting in the new plugs and wires tomorrow and I'll post those findings after the rain stops! I think my problem is the ignition wires, though. Mine have wood screw type connectors in non-solid core Beru wires and the ends about fell off when I removed them. It makes sense now, looking at my plugs.

fingers crossed!
David

dsmith

Well, new wires and plugs cured my symptoms. I still need to clean the distributor and replace the coax wire when it arrives, but that's it, unless the cause is deeper. I drove with a 13.5:1 AFR and had some popping on decel. I raised it to 14.5:1 and it ran quite well.

I now know how to adjust my WUR and FD, set AFR and build a set of wires. Now, maybe I can learn how to drive it! And parts cost was $93 for Bosch wires with Beru connectors and $12 for plugs. I don't count tools.
Thanks to all,
David

Mike Murphy

That's great news, David! But I'm surprised. I guess I don't understand how wires and plugs would cause an engine to run lean. If anything, bad wires and plugs might cause misses, thus leaving an unburned air/fuel mixture to escape out of the cylinder. I would think that would cause a rich condition, since leftover fuel would be in the cylinder for the next combustion cycle.

Maybe if I knew what WUR, FD, and AFR meant, I would have the answer!

Anyway, it's good that you're fixed