Need help tracing a misfire

[MrT]

I was gonna buy all the bits tomorrow, so hadn't really looked into the problem, but out in it today, the intermittent misfire got so bad it was dangerous to drive. I managed to buy points (they were completely worn out!) and condenser, but that hasn't cured it, and I can't get any other bits locally. The leads appear to be arcing badly, so maybe that's the cause of the misfire? It idles reasonably, and you can rev it at rest fine, but when you try to drive and put the engine under load, you're going nowhere...

Dale

'64 Austin A60 pickup
'81 Triumph TR7 FHC
'87 Yamaha SRX-6
'88 Yamaha SRX-6
'98 Kawasaki ZX-7R
'98 Ford Maverick SWB
'04 Fiat Idea

[Underdog]

By leads I assume you are refering to the plug wires? Shouldn't be getting arcing...perhaps time for a new set. My boat engine exibited the same symptoms and although the wires looked fine, a new set cured the problem.

72 MGB BRG
80 TR8 Persian Aqua
If women don't find you handsome, they should at least find you handy.

[Cobber]

<font face="Comic Sans MS"><font size="2">You shouldn't have the HT leads arcing so chuck the things in the bin while ya at it have a good look at the dizzy cap and rotor button/arm if they look at all suspect replace 'em too, it's not worth the trouble of buggerising around with crappy ignition components. If you trouble persists you might wanna ditch the coil another thing you might wanna check is for wear in the dissy shaft if it and the bearing surface of the dissy is worn (AC Delco dissy's are good for this) that may be a cause of misfire and if the dissy is bloody Lucas, then the plate that the points attach to may be loose and floggin' around. </font id="size2"></font id="Comic Sans MS">

80'Triumph TR7, , 73'Land Rover (Ford 351. V8),
'89 Ford Fairlane
85'Alfa 90, 69'Ford F250.
76' Ford F100

[MrT]

I'll be buying everything new tomorrow at Stoneleigh, it just means I can't go in the 7...

'64 Austin A60 pickup
'81 Triumph TR7 FHC
'87 Yamaha SRX-6
'88 Yamaha SRX-6
'98 Kawasaki ZX-7R
'98 Ford Maverick SWB
'04 Fiat Idea

[REPLIC8]

Also check the fuel filter & see if it's full of brown crap. If so your tanks probably rusty. My TR8 has a bad misfire even after replacing all the leads, plugs etc. The wise fellows on this forum suggested rust in fuel as the problem, & on inspection, yes my tank is rusting. I'll be sorting it during the planned rebuid starting later this year.

Andy
1981 UK SPEC TR8

[MrT]

Well there's no fuel filter in the engine bay, though that's not to say there's not one near the tank. Both float chambers were pretty cruddy in the bottom - when dry, it's a really soft/fine tan colour powder...

'64 Austin A60 pickup
'81 Triumph TR7 FHC
'87 Yamaha SRX-6
'88 Yamaha SRX-6
'98 Kawasaki ZX-7R
'98 Ford Maverick SWB
'04 Fiat Idea

[Beans]

Presuming your car has the original fuel pump.
There is a filter gauze inside the pump that can get clogged up with muck


<center>
<font color="blue"><i>1981 TR7 FHC Sprint (better known as 't Kreng)
1981 TR7 DHC (now completely dismantled)
Also a 1980 TR7 DHC, 1980 TR7 DHC FI, 1981 TR7 FHC</font id="blue">
<font color="red">http://tr7beans.blogspot.com/</i></font id="red"></center>

[busheytrader]

[quote]<i>Originally posted by MrT</i>

Well there's no fuel filter in the engine bay, though that's not to say there's not one near the tank. Both float chambers were pretty cruddy in the bottom - when dry, it's a really soft/fine tan colour powder...
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

Hi Mr T,

The exact same thing happened to me and I'm certain your problem is fuel starvation. That powder comes from the tank rusting from the inside out and it will eventually leak out from the bottom.

I had an inline filter mounted upstream of my carbs and it was full of your tan powder. It allowed enough flow for the engine to idle and accelerate slowly but anything above that made it pop and bang and lose power.

It's unlikely that the pick up in the tank has become clogged. I think the standard 7 fuel pump incorporates some sort of filter but I'm not sure as I've been V8 equipped for too long. Either way you'll need to flush this stuff out of your pump and carbs etc and fit a quality high flow fuel filter between tank and pump. Then it's a question of how long it takes before you're forced to replace the filter or tank or both.

Checking out the electrical components after flushing out the rusty powder is a good idea as well

Cheers,


Adam

TR7 V8 DHC Jaguar Solent Blue. 9.35cr Range Rover V8, Holley 390cfm, JWR Dual Port, 214 Cam, Lumention, Tubular Manifolds, Single Pipe Exh, 3.08 Rear, 200lb Spax & Solid Bushes, Anti- Dive, Granada Vented Discs & Calipers, Braided Hoses, Green Stuff, 4 Speed Rear Cylinders, Uprated Master Cylinder & Servo, AT 5 Spokes and Cruise Lights. No Door Stickers. Mine since July 1986, V8 from 1991

[jeffremj]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">The leads appear to be arcing badly, so maybe that's the cause of the misfire? It idles reasonably, and you can rev it at rest fine, but when you try to drive and put the engine under load, you're going nowhere...<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">If the leads were OK and you still had this problem when under load, then it is sure sign that the spark plug gaps are too 'big'.

[MrT]

The fuel pump is a sealed affair, not the type held together with 6 small screws, so I can't dismantle it, though I will flush it through with WD40 with the pipes off, then fit an inline fuel filter before the pump (I'll get one tomorrow).

I spoke to Simon at Robsport today - I'm ringing him tomorrow and he's gonna send me a cap and leads gratis (you should see how much it's arcing in the dark [:0] ). I'll get a pair of carb gasket sets off him too, that way I can make sure the fuel system is as clean as I can get it without a new tank (yet!). The ignition system is on its last legs, but the fuel systems filthy (probably through lack of regular use over the past few years as much as anything), so I reckon it's a combination of both causing the problem.

Strange sparkplugs in this one - NGK's, I think, but with three curved-nosed electrodes (kind of remind me of Golden Lodge plugs from my Alfa days...), so I can't see how they can be accurately gapped. All were the right colour, so I cleaned and refitted those.

I don't get to see much daylight in the evenings after work, so I guess I'll be busy next Saturday...

Thanks for the pointers,

Dale

'64 Austin A60 pickup
'81 Triumph TR7 FHC
'87 Yamaha SRX-6
'88 Yamaha SRX-6
'98 Kawasaki ZX-7R
'98 Ford Maverick SWB
'04 Fiat Idea

[Beans]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by MrT</i>

The fuel pump is a sealed affair...<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
Original (mechanical) pump has a screw on top which gives you access to the filter.
On the type you are referring to (with the 6 bolts around the casing) you can renew the pumps membrane/diaphragm.

<center>
<font color="blue"><i>1981 TR7 FHC Sprint (better known as 't Kreng)
1981 TR7 DHC (now completely dismantled)
Also a 1980 TR7 DHC, 1980 TR7 DHC FI, 1981 TR7 FHC</font id="blue">
<font color="red">http://tr7beans.blogspot.com/</i></font id="red"></center>

[MrT]

Ah Ok, cheers - I'll check that out too.

Dale

'64 Austin A60 pickup
'81 Triumph TR7 FHC
'87 Yamaha SRX-6
'88 Yamaha SRX-6
'98 Kawasaki ZX-7R
'98 Ford Maverick SWB
'04 Fiat Idea

[Hasbeen]

MrT, if your petrol, & tank are dirty, & full of muck, clean the
tank out. Dirty fuel can give your misfire, or total stopage. It is
a waste of time, cleaning the system, if the tank is full of muck.

It can be done moderately successfully, through the fuel gauge
sender fitting, with the tank remaining in place.

When I put my current 7 back on the road, it was blocking an inline
filter in less than 200Km driving. After cleaning the tank out, a
filter lasted a couple of months, probably 1500Km. Unfortunately the
tank only lasted a few months, before pin holing with rust from the
inside.

With the tank at or below 1/4 full, simply jack the rear of the car
reasonably high, with one side 3" or 4" higher than the other.
Remove the sender. With a 1/2" tube, siphon the contents of the tank
out, from the lowest corner, into a container or two.

Strain a couple of gallons of this old fuel, pour it back into the
tank, & re-siphon this out. Repeat this process, until you stop
getting rust & water from the tank. I got a cup full of dirty
water, & an egg cup full of rust out of mine.

Hasbeen

[moestr7v8]

If you are getting a new fuel filter get the type that you take apart and clean at least that way it gives you a bit of leeway before replacing the tank,which will be inevitable if you have got that much crud in the fuel line.
Contact T.D.Fitchett you will get everything you need ie tank straps foams bolts etc at a very good price and very fast delivery when I ordered the one for Esthers 7 it was the best deal pricewise and delivered the next day. [8D]
Regards
Moe

[jeffremj]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Strange sparkplugs in this one - NGK's, I think, but with three curved-nosed electrodes (kind of remind me of Golden Lodge plugs from my Alfa days...), so I can't see how they can be accurately gapped. All were the right colour, so I cleaned and refitted those.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">Interesting if the colour is OK. The multipronged items are not nomally re-gapable (IIRC). The gaps are usually bigger than is recommended for a normal TR7. If the gap IS too big, you will get arcing elsewhere and misfire under load.