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Red motor fuel pump diaphragm split?
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I had a bit of work done on my 186, nothing major, total rewiring and a couple of Strombergs. Its been starting and running fantastic for over a year. The other day I ran around for 20 minutes and fueled up at a servo. When I left the servo it was running like a pig 100 metres down the road and I just managed to limp 5 mintues home. I thought dirty fuel or I used diesel. I went back to the servo and checked and it was 95. Next day it was reluctant to start so I splashed some fuel in the carbys like I have been doing for 40 years and it started and ran fine. I didn't go for a drive but I ran in the driveway for half an hour until the new electric fan came on. I figured dirt or vapour lock or something. This morning it started instantly and ran perfectly. But I noticed a lot of bubbles in the glass fuel pump bowl (that was NOS), it was running so nice I took it for another drive and after 15 minutes I could tell it was starving for fuel and it cut out so I had to get a mate to tow me home (embarasment+). Today I had a fiddle around and couldn't see anything wrong other thant the accelerator pumps not doing anything. I disconnected the fuel line and turned the motor over a few times and it didn't seem like much fuel pumped into a cup. So I filled the float bowls with a syringe and it started and ran perfectly, but there were all those bubbles in the the fuel pump glass bowl that caught my eye yesterday. I'm wondering if the diaphragm is split. I had that a couple of times with red motor V8s that don't have th glass bowl fuel pump, but they leaked oil when they failed. Does "The Knowledge" think its a split pump diaphragm, or could there be something wrong with the vey-old fuel tank pick-up? https://photos.google.co...7eWrqhq4-yqP8BxzldirCgnCEdited by user Sunday, 15 October 2023 8:21:13 PM(UTC)
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how clean is the fuel filter? when was it replaced? Edited by user Sunday, 15 October 2023 9:10:03 PM(UTC)
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You can pressure test the fuel pump. Some of the basic compression tester gauges can do this.
Just connect the gauge to the fuel pump using hose clamps and fuel hose/line.
HQ/HJ 202 book says 3-4psi.
I sometimes see a few bubbles under the glass but never very many and usually none.
The fuel pumps can last a long time. I bought a replacement fuel pump because I figured the old one had to be wearing out after so many decades. Nope, it tested fine. The replacement pump is still sitting on my shelf!
It might also be a soft hose somewhere. The hose can pull itself inward and cut or reduce the fuel flow. Usually more common when the hose is warm or hot, or when you accelerate or use high revs as more fuel gets used and it starves. The engine will usually idle fine when this is the problem.
Good luck.
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I just removed the glass bowl and gasket. Cleaned up the surfaces and the gasket (which felt pretty hard). Tightened the bowl up real tight and no bubbles. I ran it for 15 minutes and no issues, but that caught me out twice! The bowl looks to be 3/4 full and I'm sure it was 1/4 full when it cut out. I hate getting towed. (edit: the gasket is rubber not cork.) Edited by user Monday, 16 October 2023 4:59:23 PM(UTC)
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Joined: 22/05/2021(UTC) Posts: 21 ![Australia]( "Australia") Location: Perth Thanks: 2 times
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Rank: Member
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Joined: 22/05/2021(UTC) Posts: 21 ![Australia]( "Australia") Location: Perth Thanks: 2 times
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Dammit, I went for a drive today and it did the same thing after about 20 minutes. The fine bubbles were fixed with a bowl seal, but when it warms up, more and more large bubbles come through the inlet. I thought it might be vapour lock so lowered the temperature the electric fan comes on and wrapped the fuel pipe near the engine with heat wrap. No success. I managed to limp home by pumping the accelerator, it was gasping and backfiring. When I got home it would barely start and I wondered if it was electrical, so I put a timing light on it, the light kept flashing as the engine was cutting out. As soon as it cooled down it ran perfectly in the driveway for ages, so I doubt its a blocked filter. So I'm back to thinking the diaphragm warms up and goes soft and leaks. While I was trying to start, I'm sure I could see the fuel level in the bowl jumping all over the place, but it was hard to see from the cab. I tried tightening the screws around the pump. I have an old school vacuum/pressure guage so I will give that a try. Part of the problem diagnosing is that the engine doesn't get hot with the bonnet open.
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Originally Posted by: Agrid  Part of the problem diagnosing is that the engine doesn't get hot with the bonnet open. Not a problem I've seen before, are you running a good thermostat & do you have an accurate temperature gauge ? Dr Terry |
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Joined: 22/05/2021(UTC) Posts: 21 ![Australia]( "Australia") Location: Perth Thanks: 2 times
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Being a 38 Willys Coupe there is very poor airflow over a small radiator. I guess this is why they added vents to the 39-41 models. Its a 186 with twin Strombergs and the thermostat is new and working well. I have a new temperature guage and warning light on separate senders and of course the digital readout on the thermatic fan. Today I ran it in the shed for ages and tried to get it pretty hot. Once it warmed up enough with a couple of cycles through the electric fan turning on. The guage near the back of the motor was showing 95 and the radiator about 75. I then disconnected the fuel hose and plugged in my ancient pressure/vacuum guage (see attached, don't laugh). It showed a little over 3 psi from the pump. The car ran on fuel in the twin strombergs for about 30 seconds so I got it give it a few revs. The pressure was stable. Interestingly, there were no bubbles in the fuel pump bowl. I reconnected everything and started and the fuel pump was bubbling like crazy, but the car kept running fine. Almost like the inlet side of the fuel pump bubbles as it works to fill the fuel bowls. I've never been able to get the car to cut out while running at home, its only after driving around for 20 minutes or so. It cuts out runs for a bit if I pump the carb. If it cuts out and I let it sit for a a few minutes it starts and limps for a short distance. Once I got home it ran in the driveway for ages. Now I'm wondering if it is vapour lock in the carbs, I remember it was a thing in the old days but I never experienced it. Maybe an electric fuel pump will help? https://photos.app.goo.gl/azNjWzkJNJ3GgVB78Edited by user Tuesday, 6 August 2024 8:22:26 PM(UTC)
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There might be something blocking the fuel coming from the tank. Maybe send compressed air back down the lines from the pump to the tank to clear them? Or try testing the suction pressure on the other side of the pump? If the fuel isn't feeding into the pump freely, maybe the pump is cavitating the fuel causing the bubbles. It sounds a bit too regular to be a plastic bag or something similar in the fuel tank covering the fuel pipe but this does happen and can be confusing. Has the fuel tank been cleaned recently? Maybe crap gets stirred up as you drive around and clogs the tank uptake. If you have the time taking a photo of the pump and lines might let someone on the forum spot something. Dunno, maybe!! HTH. EDIT: Just noticed the fuel intake line runs under the dizzy and (I assume) right next to the block. This is a very hot place for it. Maybe run it over by the mudguard to keep things cooler. You could check that fuel line to see if it is a bit degraded/cooked. Edited by user Wednesday, 7 August 2024 6:38:58 PM(UTC)
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Joined: 22/05/2021(UTC) Posts: 21 ![Australia]( "Australia") Location: Perth Thanks: 2 times
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^ Yeah thanks, the fuel pipe comes away from the mudguard at right angles, maybe from when it used to have a grey motor. I had the flexible hose made up to the same length as the previous one, I should have had it made shorter.
I've seen elsewhre that people had sat the Strombergs on spacers, maybe I should look into that as well.
Or send it out for an electric fuel pump.
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Red motor fuel pump diaphragm split?
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