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| carburetor | Rate Topic |
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| Posted: 11-14-2018 09:54 pm |
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1st Post |
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jomac Member
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recently drove my JH. i notice engine ran a little rough while cruising in high gear. air temp was about 30 and engine was running below halfway mark on the temp gauge. later i did a performance check thru all gears. afterwards, the engine loss power and stalled. i pulled over on the shoulder and stopped. i then turn off the ignition and then promptly restarted the car and drove home like nothing happen. could this be a sticky carb float valve? any suggestion. latest update: First thank you all for responses and help. i traced it down to my positive wiring connection to the battery. last year i bought those quick disconnect battery terminals (junk). well the cheap way they secure your cables are with none locking nuts and those worked their way loose causing intermittent power.. i replaced it with standard terminal for multiple cable attachments. (i have fused relays on all my main components.. lights, starter and fuel pump that power directly from the battery.) latest update 2: well it did it again but this time i put the car in neutral and pump the gas, keeping the engine running rough. It cleared itself out and ran normal. it sounded like engine was starving for fuel. i discovered that it was the temp compensators are faulty. which makes sense cold engine doesn't need more air. so i shut them both off and let the engine cool down and retested car. problem went away! Its in the twenties here, causing the problem to show up rather in the warm months. Last edited on 11-19-2018 06:12 pm by jomac |
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| Posted: 11-15-2018 03:13 am |
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2nd Post |
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Tom Bradley Member
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If one of the carbs is malfunctioning I would expect that the corresponding pair of spark plugs would show some evidence of too rich or too lean mixture while the other pair would not. Intermittent problems like this are often caused by bad electrical connections. Doing the described performance check (revving up to high RPMs?) can make loose connections worse. Check that there are no loose connections in the ignition primary circuit as well as loose HV cables and loose distributor cap. If you have a pertronix ignition and high-power coil then bad spark plug cables or plugs can cause the spark to jump to other places, causing damage to the distributor cap. Do you know what this damage looks like? It is often tiny and hard to find. Replacing the distributor cap may be a good idea. I have read that the pertronix ignition is sensitive to electrical interference. Make sure you have resistive plugs or cables. Do you know if your voltage reading was OK when this happened? I once had a Lucas alternator that cut in and out after the engine warmed up that caused ignition problems. Intermittent problems are very frustrating. Tom
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| Posted: 11-15-2018 03:57 am |
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3rd Post |
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jomac Member
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Tom I have e3 3.46 model spark plugs, all plugs look good. using magnecor 8mm wire, they look good bought them 3 years ago... 3000 miles usage. last july i replaced the pertronix ignitor it started failing. Inspected the rotor and cap both looked like new. I am using the pertronix matching coil, its voltage checks out on bench test... but loose connection could be issue. which HV cables are you referring too?. The alternator is a new , bought last year a 35 amp one for about 70 bucks. it show 14.5 + output while driving. Going to check the fuel tank for loose particles. the tank was in poor condition when I got the car. Cleaned it and coated it with an epoxy kit sold at motorcycle shops. I'll drive it tomorrow and see it reoccurs. weather permitting.also, i have an electric fuel pump with an low oil pressure switch to cut fuel to the engine during an accident, that would cause the engine of shut down by shutting off the fuel pump? Last edited on 11-15-2018 09:28 pm by jomac |
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| Posted: 11-16-2018 02:23 am |
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4th Post |
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Tom Bradley Member
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The HV cables I mentioned were the high voltage cables from the coil to the distributor and to the spark plugs. The magnecor cables should be OK. The spark plugs are questionable. According to the e3 web site the 3.46 plugs are equivalent to the N9Y plugs in the JH manual, but they are not recommended for the JH. My guess is that the fixed gap is larger than the 0.025" gap recommended for the JH. Since the web site did not specify the gap I don't know if it is large enough to cause reliability problems or not. For debugging purposes I would use a standard plug gapped to the specified 0.025". Once everything is running reliably, then you can try out plugs with larger gaps. Do you have a fuel filter in line? I have one with a clear case installed just before the fuel T. It makes it easy to see if there are any contaminants coming in from anywhere. This is the first time I have heard of an oil pressure switch for turning off the fuel pump. I have no idea how reliable it would be and how to make sure it is not cutting off power to the pump when it should not. If in doubt, I suppose bypassing it temporarily would rule out that cause. Tom Last edited on 11-16-2018 02:24 am by Tom Bradley |
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| Posted: 11-16-2018 06:55 pm |
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5th Post |
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Esprit2 Member
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Jomac, Your first message sounds familiar to me. For starters, replace the fuel filter, preferrably with a large one. Then inspect the contents of the old filter. If it's empty (no collected debris), then I'm barking up the wrong tree. Ignore me. If there's a lot of debris, enough to inhibit flow through the filter, and if the engine now runs better with the new filter installed, then we're on the right track. If there's a lot of debris present, much of it rust colored, then the fuel tank is rusty/ crusty inside. Continuing to replace the fuel filter with large ones will help put-off the inevitable, but the real fix is to remove the tank and either have it cleaned out and coated inside, or replace it. Also, remove the carbs' top covers and inspect the float bowls for flakes rust-dust. "Any" is a bad sign, it doesn't have to be a significant build up. If there flakes present, then remove the carbs for a good cleaning. If crud is in the bowl, then it's also in the rest of the carb where you can't see it. *~*~*~* I once had a 'strong' 907/ Dellortos suddenly start running like it had a built in speed limiter. When cruising on the freeway, it would run normally at speeds below 63 mph. At 63+, the engine would begin to lose power. The more I stepped on the throttle pedal, the worse it got. Once started down that path, lifting off/ slowing down would not help. The engine would slow to the point that I had no choice but to pull over to the side of the road. Given a few seconds to catch it's breath, the engine would soon start to 'pick-up' and run normally again. It would accelerate back out into traffic, it could cruise at 60 mph for miles without a problem, until the speed touched 63 mph again. Repeat, repeat. Removing the carb covers revealed rust dust. Checked the filter, and it was full of rust dust. The fuel lines, Flowlok valve and aftermarket inline fuel pressure regulator all had rust dust in them. When I opened the aftermarket fuel pressure regulator, it was packed so full of rust mud that it made a perfect impression of the inside of the housing. It was like opening a mold. The pump was only able to push enough fuel through all that mess to support 63 mph. Period, no debate. I did a comprehensive clean-out by opening/ cleaning/ re-assembling the carbs, SU fuel pump, Flowlok valve and pressure regulator, plus replacing all fuel lines. Two large (fuel injection size) fuel filters were installed, one at the outlet of each fuel tank (Esprit has two tanks) and prior to the SU fuel pump, and a third smaller filter as close to the carb inlets as possible. That band-aide fix, plus regularly checking and replacing the filters, worked for the short term and the car's top end performance was restored. However, the real fix required fixing the tanks. I'm guessing that's what you're facing now. Regards, Tim Engel Last edited on 11-16-2018 06:58 pm by Esprit2 |
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