Help needed, Losing Power when over 50 mph.

Sausage · Aug 25, 2024

Hi all!,
I am having an issue with the engine and need some advice. So it drives fine around town but as soon as i get it onto the dual carriageway and the speed gets above 50 mph ish the engines starts hesitating and i start losing power. I have to drop the speed back down to the 40’s to be able to drive it. It only started happening about a week ago and it’s been good runner for years previously. It’s a stock 1600 with a genuine Solex Pict 34 carb [rebuilt around 8 years ago], stock fuel pump, 009 Dissy and oil bath air filter.

Since then i fitted a new accelerator cable as the old one was about to snap. I am getting full throttle so it’s adjusted correctly.
I replaced the fuel filter and gave it a service/tune:
Adjusted tappet clearances [0.15 mm].
Cleaned and adjusted spark plugs. [Plug gap. 0.70 mm]. All were dry and black/grey.
Checked points gap [0.40 mm],
Retimed engine to 30 degrees at 3500 rpm.
Went for a test run and but it was still happening.

Next I replaced the HT leads and put in new Spark plugs, went up to the dual carriageway again but no difference.

What do you all think could be the issue? Thanks in advance, Pete.

ozziedog · Aug 25, 2024

Hi Pete. Let’s have a go at the freebies first. Fuel pressure check. Empty one and a half or two litre clear drinks bottle. Disable the engine with rotor off. Take fuel pipe off carb and pop it in the bottle a couple of inches and lay the bottle on its side. Have an assistant glamorous or otherwise crank the engine over for two or three seconds while you hold the pipe in the bottle. The fuel should spout almost to the bottom of the bottle like a fourteen year old young un. Let’s make sure we are getting enough fuel through to the carb.

Ozziedog,,,,,,,,,,,, you need fuel firstly

Sausage · Aug 26, 2024

Thanks Ozzie! I have just tried it and the fuel was squirting about 4 inches into the bottle from the end of the fuel line. It seemed to be coming out pretty well. Does that sound about right? And if it does, what do you reckon to try next?

ozziedog · Aug 26, 2024

No it don’t sound brill, it should be gushing to the bottom of the bottle well at least well past half way. So it sounds like it might possibly be fuel starvation when you need it most at full throttle. I’d check the fuel to the pump next by just taking the fuel pipe off the pump and lowering it with your finger over the end into a bowl or small container and see how your flow is. If the flow is real good I’d be looking at your fuel pump, if it’s crap, I’d try taking the fuel cap off to see if it improves. Go careful with all this petrol sloshing about. Also have a look for old petrol filters that may be blocked that might be hidden up and around the gearbox etc etc.

Ozziedog,,,,,,,, Hope it’s this simple.

67panel · Aug 26, 2024

And the gauze filter in the tank, have found them collapsed.

Sausage · Aug 26, 2024

ozziedog said:
No it don’t sound brill, it should be gushing to the bottom of the bottle well at least well past half way. So it sounds like it might possibly be fuel starvation when you need it most at full throttle. I’d check the fuel to the pump next by just taking the fuel pipe off the pump and lowering it with your finger over the end into a bowl or small container and see how your flow is. If the flow is real good I’d be looking at your fuel pump, if it’s crap, I’d try taking the fuel cap off to see if it improves. Go careful with all this petrol sloshing about. Also have a look for old petrol filters that may be blocked that might be hidden up and around the gearbox etc etc.

Ozziedog,,,,,,,, Hope it’s this simple.

I took the fuel line off to the pump and it’s coming out nice and fast so am going to get a new pump, Bakelite bit and pushrod tomorrow. Fingers crossed this will be it. I will update later this week when fitted and tested out. Thanks for your help!

matty74 · Aug 26, 2024

Go easy with the Bakelite pedestal, as they can break easy. If the rod is freely moving up and down and the correct length I’d be tempted to just go with the pump change first. The quality and bore of some of the replacement pedestals ain’t too great, there’s a thread over on LB discussing this.

A tell tale sign of the pedestal being broken is if you can hear a ticking noise coming from the fuel rod when engine’s running.

Here’s a broken original, luckily I was able to salvage the broken piece

ozziedog · Aug 26, 2024

matty74 said:
Go easy with the Bakelite pedestal, as they can break easy. If the rod is freely moving up and down and the correct length I’d be tempted to just go with the pump change first. The quality and bore of some of the replacement pedestals ain’t too great, there’s a thread over on LB discussing this.

A tell tale sign of the pedestal being broken is if you can hear a ticking noise coming from the fuel rod when engine’s running.

Here’s a broken original, luckily I was able to salvage the broken piece

As Mattie says above, these new pedestals have got some extremely nasty and anti social bad habits, like pinching your pumps pushrod when they get warm or oil soaked. Measure your pushrod and make sure you get the same length, there’s two different ones from memory and probably made of stiff toffee or assorted Chinesium , so keep your old un as spare.

Ozziedog,,,,,,,,fingers crossed.

creationblue · Aug 27, 2024

Have you changed your coil?

W1K1 · Aug 27, 2024

be careful with reproduction pumps, they should be around 3PSI, I have had repro pumps put out 10-12 PSI. Then you have to stack gaskets, or cut the piston to get a proper fuel pressure, not ideal. your best bet is to put a pressure gauge inline and see what it's putting out when running. most auto suppliers have the vacuum/pressure gauge kits for $20 or so

Sausage · Aug 27, 2024

creationblue said:
Have you changed your coil?

Not so far but i have a spare one so waiting to go.

creationblue · Aug 27, 2024

most likely cause I'd say, I had something similar years ago and changed fuel pump, changed it again for an electric one, went electronic points etc and made no difference. Then one day I broke down, got recovered home and changed the coil and been fine ever since

Sausage · Aug 28, 2024

I fitted the new fuel pump, push rod and gaskets and tested the pressure again and it was definitely higher, around twice as far as previously in the bottle test. I took it out for a test run this morning and the same issue is still there and seems to be getting worse each time as i didn’t even get to the dual carriageway this time.
Before I left, i tested the coil with a multimeter, 3.6 ohms across positive and negative and 8300 ohms from centre coil to a terminal.
I tested the coil again when I got home, about 20 mins after the hesitation happened, and got a reading of 3.9 ohms across positive and negative and 9100 ohms from centre of coil to a terminal.
From what I have read those figures seem fine but the second readings were taken quite a while after it would have been hot and under load.
So I am going to change the coil for the spare one and try it again.
If swapping the coil doesn’t work, does anyone have any other ideas?

static · Aug 28, 2024

Yes: swap distributors.

ozziedog · Aug 28, 2024

I’m sticking with the freebie checks so far. Did you say you’ve changed your condenser? My next freebie is to open up your 009 and have a little look at the springs undeneath the points plate and just wiggle it all about in there, I’m thinking it’s possibly not advancing or it’s seized in there with rust.That might slow down your high speed stuff a tad.

Ozziedog,,,,,,,,,, Bag your good spares and write a memo with them.

Sausage · Aug 29, 2024

I changed the coil for the old spare one and it made a big difference, i got up to the dual carriageway and cruised at 55 for around 4-5 miles with no issues so i thought i would push on to the hilly bits and then as going up a long hill the hesitation came back.

I will replace the condenser and points today with the spares and check out the insides of the distributor and test it out again with fingers crossed. Thanks for everyone’s help so far! Pete

Sausage · Aug 29, 2024

I pulled the Dissy out, it looks in pretty good condition inside. There are 2 weighted bits inside, i can lever one so it hits the stop [the one on the left hand side in the pic] but the one on the right wont hit the stop when levered with a screw driver. Is that normal? Is one for max advance and one for min advance?

creationblue · Aug 29, 2024

Im pretty sure you want to use a SVDA distributor to get the best out of your engine. A coil is nearly aways the issue, glad you git it sorted

sparkywig · Aug 29, 2024

Sausage said:
I pulled the Dissy out, it looks in pretty good condition inside. There are 2 weighted bits inside, i can lever one so it hits the stop [the one on the left hand side in the pic] but the one on the right wont hit the stop when levered with a screw driver. Is that normal? Is one for max advance and one for min advance?

Both weights should move freely, so this could contribute to the hesitation.

ozziedog · Aug 29, 2024

Sausage said:
I pulled the Dissy out, it looks in pretty good condition inside. There are 2 weighted bits inside, i can lever one so it hits the stop [the one on the left hand side in the pic] but the one on the right wont hit the stop when levered with a screw driver. Is that normal? Is one for max advance and one for min advance?

While you’re peaking in there, sneak up on the pivotty bits with a shot of 3:1 oil or anything lubbey that comes to hand, dipstick might do as it’s just next door . As Sparky Wig says they should both move easily and freely. I’m wondering if it’s your main lead not getting right in there, either in the coil or in the dissy. Funny how you fiddled about with it and it was fine for a while?

Ozziedog,,,,,,,,,,condensor ? You changed that dint you ?

Help needed, Losing Power when over 50 mph.

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