Help! Ongoing fuel delivery problem

[Westie73]

Hi guys

I have a coupe VX. I am embroiled in the never-ending search for reliability. I have had a problem with what I believe is a fuel issue, with a nod to a spark problem, for about 3 months.

The car has undergone trips up to Northampton Motorsport on 3 occasions now. Firstly last October they popped it on their rolling road, overhauled the carb, and tuned to suit. This solved a fuel pressure problem that I was having at the time.

About six weeks later, my exhaust downpipe started to blow, I ordered an SS replacement, but seeing as I have to use the car most days of the week, I had to have the existing one welded. While in a local (until then, trusted) garage, I asked them to also check the plugs, and change the oil and oil filter. With the job done I collected my VX. On the drive home, after about 10 mins there was a massive plume of smoke, like an engine giving up, out of the exhaust. I found out that they had overfilled the oil. Gutted, I had the car collected, they drained the oil, checked out the compression, filled the oil correctly, and clean up my engine bay.

A few weeks later, until just after Christmas, the VX started to have an engine juddering problem. I would be driving along, the car was up to temp, and at that time, I would get up to 5000rpm in 4th or 5th then I would get a severe engine juddering, ie, the revs would drop away, and it would come in and out, until I applied the clutch. I decided it needed to go back to Northampton Motor Sport because I assumed that the carb had been contaminated with oil and required another tune on their dyno. They did this, but also found that there was a fuel pressure problem due to a faulty fuel pump. They spent a number of hours checking it out, and eventually fitted a competition pump, and as far as they were concerned the problem was solved. I collected the car last weekend, and basically broke down on the way home after about 10 mins of driving. I managed to get her going and back to Northampton MS. They kept the car back, and we discussed the possibility of an electrical problem. During this past week, they fitted a competition ignition switch and a push button start, after believing that they had identified faulty ignition switch. And again told me that the car now drove beautifully, and without issue.

On my way home today, I have had all sorts of problems. The original problem is now quite bad. The VX idles beautifully, there is no issue with the ignition, I have also had a full SS system fitted, so along with the new fuel pump, the car runs, when it runs, very smoothly. However, the fuel delivery problem, or whatever it is, is back with a vengeance. The car gets up to temp no problem, then it starts to judder, with revs dropping away, I have to apply the clutch, rev her up again, and pop back under load. Driving around town, there does not seem to be a problem. Going up hills does seem to exacerbate the problem. My dad followed me home from Northampton today, and witnessed gear change flames coming from the exhaust, ie unburnt fuel igniting. Therefore I believe that the throttle and carb may be woking as they should, but that the fuel is not being ignited as it should. Can anyone please help, or shed some light on this.

Best regards
Damian

[rossocorsa]

I'd check the ignition circuit especially the sensor in the distrubutor the wires may be frayed inside and arcing common issue, other than that I've no idea best wait for an expert to come along on here with a better answer

[Westie73]

Hi rossocorsa

Thanks very much for your post...I'll check out what you suggest.

Best,
Damian

[WestonE]

Damian

This is a tough one Troy and Steve at Northampton MS are VERY experienced mechanics/ engineers. I have used them for Mapping an Emerald ECU.  I cannot offer a diagnosis from what you describe, although my money would be on a coil or amplifier breakdown with temperature.
I am potentially willing to lend you some parts that I know are in top condition if they work for you you can buy them if not you know those areas are not the problem. You can then eliminate Distributor/Cap/Rotor/Leads/Coil/Amplifier/Plugs and Carb.

Basicaly I have a mint distributor (new Hall pickup new Vacuum advance) with new coil pack,cap & Rotor and new Magnecor KV85 leads and a New Old Stock VX Carb all tried tested and driven. Can you get the car to High Wycombe? 
There is also a new K&N panel filter and a hybrid VX IE airbox with all the correct fixings to hold it to the engine for some great advantages.

My Fuel Injected Volumetrico conversion does not need the carb/aircleaner or distributor set up so I will eventually get round to selling it.

Eric Weston

[Westie73]

Hello Eric

Many thanks for your reply. I agree with what you say about Steve and Troy at Northampton, they have been genuinely decent and helpful with regard to this problem so far, and although they have not been able to identify the main issue, I cannot complain about the work that they have undertaken. I have though spent £1800 with them, without final resolution.

I am based in Beaconsfield so a journey over to High Wycombe is not a problem. To go into a little more history, I have recently had a new coil fitted, also a K&N filter element, the Magnecor KV85 leads, and two sets of spark plugs in the last 6 months. Not only that, but Steve also replaced the dizzy cap, and the rotor arm for me. The original distributor is still on the car however, as is the carb. I am not available to get the car over to HW until later this week, but as you can imagine, I am desperate to sort this problem out.

Please feel free to email me, if you wish at damianwest@btinternet.com and perhaps we can make some arrangements. I really appreciate your help.

Best wishes,
Damian

[HFStuart]

Damien,

It does sound like a temperature related issue. Either fuel vaporisation or something's insulation breaking down perhaps. The flames also can suggest a weak mixture (oxygen in a hot exhaust enables any surplus fuel to ignite)

I wonder when they tried to  identify the fault and thought they'd cured it, did they take it for a test drive or just put it on the rollers?

The reason being that roller work is almost always done with the bonnet up and underbonnet temperatures don't get so high.

Stuart

[WestonE]

Damien

As we discussed last night work systematicly through the steps to identify the fault. BUT fix the aircleaner intake first. Beauty is less important than getting rid of the flap than is closing off the air supply even if you break off the plastic section and tank tape your hose in place for the tests.

Your real issue really could be the SC I have heard a lot of these engine running and there should not be a hard rattle from the SC and after a lot of thought overnight I have to say urgently find someone breaking an HPE VX get the SC and get it up to GC for overhaul. Give Tony Harrisson a call and post a wanted note.

 http://www.guy-croft.com/viewtopic.php?f=7&t=132
http://www.guy-croft.com/viewtopic.php?f=7&t=331
http://www.guy-croft.com/viewtopic.php?f=7&t=1864

These links give you a view inside and what gets done on an overhaul. What is there inside to create that rattle? My guess is the bearings are shot and the rotors are hitting the casing which is why i suggest finding another and getting that overhauled.  As the SC is an airpump essentially if yours is not consistently producing the pressure due to internal friction it will feel like a cut in power possibly judder as it will mess up the carburation. Complete the steps I gave you and you will know it is the issue, but either way with that noise it will let go sooner or later.

I am sorry to give you that news.

Eric 

[Westie73]

HFStuart, sorry I did not post sooner, but thanks very much for your suggestion. I have been liaising with WestonE. It looks like we are getting there. I will obviously post up any solutions.

Best,
Damian

[Westie73]

Hi Eric

Many thanks for all of your help. We fitted the distributor (complete), and the coil amplifier. Long test today showed major improvement. The problem is still there but not nearly as bad, and only now at high revs, after reaching full running temp. The original distributor is shot to hell. Sorted out the air intake too, now a huge improvement.

I take your point about the SC. Will look into it asap. I am now not sure about the vacuum advance hose. It is essentially attached from the distributor to nothing. Can you advise?

Will now try your coil as part of process.

Hope you are well.

Best,
Damian

[WestonE]

Damian

There should be a small bore vacuum take off pipe on the rear of the inlet manifold for you to connect the vacuum advance. No existing connection suggest your existing one was broken. Expect the take off to have some form of plugged hose on it currently as the car would run lean otherwise.

I am truly glad you are making progress. I take it the fuel tank was clean of rust and scale?

Eric

[rossocorsa]

There should be a small bore vacuum take off pipe on the rear of the inlet manifold f

I might be recalling incorrectly but isn't it on the carb body at the bottom facing forwards?

[LanciaDave]

I thought it faced the rear of the car. I could be recalling incorrectly though.

Damian, I must know. Did you resolve your issue? and if so, how?

I'm quite curious, as I'm having a similar issue myself and any clues would be appreciated.

Thanks,
Dave
Oregon, USA