Severe Misfire

[types26/36]

If you really do suspect a head gasket (although I am not convinced) make up a fitting to screw into the plug hole and pressurize the cylinder with the piston at TDC with compressed air (easy if you have a compressor)
If the head gasket is leaking it will bubble back in the radiator, if you do not have the facilities then take it for a leakdown test.

[archigator]

Thanks for your insights everyone. I guess the next step is to drain the sump and see what we get...

Gary
'71 Sprint FHC
Miami, Florida

[archigator]

Okay, I ran the engine for a few minutes. No white smoke, no sweet smelling exhaust. I drained the sump (left oil filter on.) Took out just under 4 quarts of oil (a bit low actually)...no evidence of water except for 3 beads of my sweat floating on the surface of the pan... no mayo either. No sheen on the surface as I assume gas would leave. The radiator took about a pint of distilled water to top off. Theoretically, if I had a blown head gasket, that missing pint of water/green coolant would have been in my oil pan, correct?

CLARIFICATION: The oil running high up my dipstick previously appeared immediately after running the engine for a bit, but once I wiped it and re-inserted it back in to get a proper measurement, I would get a normal reading.

This leads me to believe that I may not have a blown head gasket. (Do we have a consensus?) I feel better, I think.

If so, that would leave a leaky o-ring(s), leaky vacuum line to the pop-up headlights,... or bad gas.

Tomorrow I'll check the air leaks. Then perhaps, on to the gas.
Thanks again! I really appreciate everyone's help.

Gary
'71Sprint FHC
Miami, Florida

[elansprint71]

So, the oil level was normal?
The water level was down?
Run the engine up to temperature in situ- don't drive the car, just let it get really hot and see if any fluids are on the floor, if so, what are they and where are they leaking from?
As I said before there are several types of head gasket leakage symptoms; you need to obtain all the evidence before presenting it to the jury.

After we sort out your fluids, we can progress to the cause of the ignition problem.

[archigator]

We'll reconviene after the "let the car get hot in-situ" test and I can report the result. (First I need to buy some more oil.)
The court thanks you for your service.

Gary
'71 Sprint FHC
Miami, Florida

[billwill]

My bet is on excess fuel.. Possibly a damaged or incorrectly set float in a carb or a bit of grit holding the float valve open and/or a gap in the exhaust system letting extra air in there..

[archigator]

Well, I replaced the oil and topped-off the radiator. I also took off the Weber top plates and checked the floats... all seemed okay there.

I ran the car in-place for 5 minutes. No fluids leaking onto the pavement, but now some exhaust smoke (white) leaking out of the exhaust pipe connection to the headers. Then I popped the radiator cap and saw it... small oil globules in the radiator fluid. My heart sank. Head gasket, right?

A head gasket replacement is beyond my minor mechanical prowess. How much $$$ does this operation generally go for these days? Any recommended head gasket brands? I am bummed-out!

Gary
'71 Sprint FHC
Miami, Florida

[ardee_selby]

Well, I replaced the oil and topped-off the radiator. I also took off the Weber top plates and checked the floats... all seemed okay there.

I ran the car in-place for 5 minutes. No fluids leaking onto the pavement, but now some exhaust smoke (white) leaking out of the exhaust pipe connection to the headers. Then I popped the radiator cap and saw it... small oil globules in the radiator fluid. My heart sank. Head gasket, right?

A head gasket replacement is beyond my minor mechanical prowess. How much $$$ does this operation generally go for these days? Any recommended head gasket brands? I am bummed-out! Gary '71 Sprint FHC Miami, Florida

Gary,

I see no response to your post yet. Have read through thread again...so some observations:

1.0 You wrote: "My Sprint began to backfire upon decelleration a few weeks ago.." Your leaky exhaust to headers joint would, no doubt, also allow air to be sucked in. That could well have been the source of the backfiring.

2.0 So...no water was seen in the oil & no external leaks of fluids. I see (from your other posts) you are (or have been) using a form of water wetter? If so, there are (Google) reports of some folks seeing a form of brown slime with it's use. This has confused some as being oil contamination. Could it be that you're seeing? But did you also see any bubbling?

3.0 As Brian has said, above, I think a leakdown test would now be prudent.

4.0 IF it is a gasket failure, I believe the composite replacements are a bit more tolerant of lack of flatness. Other posts show you have gotten your hands dirty. Have you access to Miles Wilkins' book? Anything concerning you about head removal/replacement would no doubt be covered by help/advice from folks on here! Take it step by step if there's no particular urgency...

5.0 BTW - What mileage has the motor got under its belt? Other work done in the past?

Cheers - Richard

[collins_dan]

Gary, I am still hopeful that it is not a head gasket. I use water wetter and have seen a couple of small oil drops, which I initially thought was coming from a very nasty overflow bottle, but now realize that it might be the water wetter. I also have a small exhaust leak due to an uneven header mating surface. It's on the list to be fixed as it does create minor backfiring on deceleration. I would start with the check for bubbles in the overflow bottle while running the engine, then the leak down test. It just seems odd that the gasket would just go. I would have expected something more dramatic to trigger an event like that, but others here would know better. Fingers crossed for you. Dan

[archigator]

Thanks guys; I'm hoping that you're right.

1. I do use Water Wetter... so maybe that is the source of my brown spots in the radiator fluid. That would be great! I had no signs of engine overheating (no high water temps on the gauge) when the car started acting up. I have an original fan with an otter switch that has always been sufficient (along with my oil cooler.) I just went to start the Sprint for my Sunday morning drive, and it misfired so badly that I barely got it out of the driveway before I turned around. When last parked the Sunday before, it ran no where nearly as bad. I hardly ever get it into 4th gear on my Sunday drive, but I don't sit in traffic either.
2. I reworked the exhaust clamp at the header/exhaust pipe joint, and now it's sealed... but I still get some backfire.
3. This weekend I also replaced a clear fuel filter that resides in the trunk (boot) between the gas tank and the recently-professionally-rebuilt mechanical fuel pump (with filter screen.) There was some linty-looking crud in the existing in-line trunk filter, but nothing to the point that it would hinder fuel flow. My misfire problem persisted even after replacing that filter with a new one this weekend.
4. I also sprayed WD-40 around the o-rings with the engine running... no discernable change in engine function. I don't think my o-rings are a problem.

I had a Fiat X1/9 years ago that blew a head gasket while being driven, and when that baby blew, there was not doubt about it! White smoke blowing out the exhaust like a crop duster! My Sprint has had no such episode, and when last parked, it ran well (except for some backfire on decelleration.) It was only on start-up a week later that it became totally undriveable.

I do have Miles Wilkin's book. I also had a professionally done valve job done about 4 years (about 4,000 miles) ago. I have about 75K on the odometer. I'll check for bubbles in the bottle and do a leak-down test. I really appreciate the forum sticking by me in what may, or may not, be my "darkest hour."*

Gary
'71 Sprint FHC
Miami, Florida

* (gratuitous Churchillian reference)

[ianf]

Hi Gary,

You don't report on vacuum pipe findings. I have recently been through a similar cycle of worry and the initial backfire (and upper engine knocking) was 3 out of 4 exhaust gaskets leaking (one had almost disapeared!). A compression test confirmed head problems unlikely. Shortly afterwards feeling relieved that all was well I got back into the car on a shopping trip and ..well it would just run. Managed 6 miles home but with massive backfire on overrun (worse than exhaust gaskets). For me the problem was easy to diagnose, the vacuum pipe had come off at the inlet manifold but sounds just like your symptoms so I would check all the vacuum pipes if you haven't fixed yet, or blank off at manifold to see if that is the problem.

Cheers, Ian

[archigator]

Thanks Ian. I did a cursory check of the vacuum hoses and fittings and found nothing, but I like your idea about blanking-off the pipe. I'll check that out as well. Thanks.

Gary
'71 Sprint FHC
Miami, Florida

[archigator]

Okay...

1. I checked the vacuum hoses off of cylinder no. 1... no leaks. In fact when I took the hose off I heard a 'whoosh' of air, telling me that the vacuum was good.

2. I ran the engine with the radiator cap off... absolutely no bubbles.

3. I did a compression test with the following results... 170-152-176-180. I poured a teaspoon of oil into number 2 cylinder and raised the compression from 152 to 167 pounds. According to the literature that came with the Compression tester:
"If a reading on two adjacent cylinders is 20 pounds (or more) lower than the other cylinders, a defective head gasket is indicated." I don't have two adjacent cylinders that are lower than the others, and I don't find water in the oil, and I have no bubbling in the radiator. Can I now reduce the odds that it's a head gasket to less than 10%?
"If the reading are low or vary widely between cylinders, pour a teaspoon of oil into the cylinder. If the readings increase considerably, the fault may be due to poorly seated or worn piston rings. If the readings remain about the same, the valves and/or associated components are likely the cause." I believe this indicates that I may have a ring problem.

However, I don't think my one low cylinder is below manufacturer's standard (borderline maybe), and I don't know that a defective piston ring would cause the sputtering and backfire that I'm experiencing. I find that I don't have the equipment to do a proper leak-down test, but I don't believe now that I have any real head-gasket symptoms. I'm pretty much stumped...


Gary
'71 Sprint FHC
Miami, Florida

[ardee_selby]

I'm pretty much stumped...Gary '71 Sprint FHC Miami, Florida

Gary,

Nil desperandum!

1.0 What do the plugs look like now? There may be some tell-tale signs of what's going on. Burning oil/running rich/running weak or whatever. Any chance of a pic?

2.0 WRT white exhaust smoke... just a thought. I assume you have a servo. So have you checked/needed to top up brake fluid level at all, since this problem arose?

3.0 Out of interest, you mentioned "vacuum hoses off of cylinder no. 1". Does that mean you also have a take-off from No.4?

Cheers - Richard

[archigator]

or a gap in the exhaust system letting extra air in there..

CAPIAMUS CEREVISIAM !*

I think Bill gets the prize! I just found a crack in my exhaust headers that I didn't detect previously. I would assume that would be logical since my initial symptoms were backfiring upon decelleration. Decelleration would logically afford the oppportunity for air to leak back in to the engine at the header crack and cause problems.

I'll see about getting my header welded, and hope that solves the problem. If it doesn't, I'll be back.

Thanks everyone for your help!

Gary
'71 Sprint FHC
Miami, Florida

* "Let's grab a beer!"