QuestionQUESTION: Have been restoring 74 TR6 for past 4 years ... now in sorting stage. Engine rebuild was part of restoration. Ran fine for about 200 miles but now goes anemic after a few miles or 15-20 minutes idling in garage. Does not stall but idles poorly and will not rev. Runs well until it just goes anemic.
I have ruled out ignition problems and obstructions in the fuel line. The fuel pump appears to function properly but replacing it is my next step.
Two things that are disturbing and may be factors are that I can't turn the engine by hand even with all plugs removed ... it is tight. And, the intake manifold temperature is no higher than 16 in. Hg at idle.
I recently ran the engine in the garage with vacuum gauge connected to the intake manifold. After about 20 min. the engine went anemic. When the engine got hot, the vacuum dropped to 13 and then lower when it was anemic. Don't know if this is cause or effect? I checked temperature shortly after shutting the engine off: intake manifold was 190 deg and exhaust manifold was 230 deg.
If I restart the engine while it is still hot it will go anemic right away. If I wait until it cools, it will go through the same 15-20 minute pattern.
Other info ... timing is set at 12 deg BTDC & vacuum retard has been disconnected; EGR valve has been removed and manifolds holes plugged; can detect no air leaks in manifold or carbs; plugs look correct or slightly lean; happens even if I close temperature compensators; plugged brake servo and still happened; temp guage is normal at slightly before midpoint of guage ... has not gone higher than midpoint; valves are set at a "loose" .010"; in December, leakdown test was normal and compression was uniform but at only 125.
What can cause my low intake vacuum? Can this cause the anemic performance? What internal engine issues could cause this problem?
Your suggestions will be appreciated,
Another Howard
ANSWER: Hi Other Howard,
If I had all your symptoms I would check exhaust back pressure. If you can't unplug the exhaust port that had the EGR and make-shift a temp plug to fit a hose to, and run the hose to either a low pressure gauge or most vacuum gauges have a small scale for checking fuel pressure. On cars that there is no plug I found that a small 2 in. piece of brake line will work by drilling a hole just a little smaller than the pipe and I drive the pipe into the exhaust pipe just after the manifold and put the hose on that pipe and start and rev the engine. You don't have to even warm the engine up because the gauge will show right away if there is a problem. I found no British car that I tested can handle more than 1 and 1/2 PSI on a high rev. GM claims some of their cars can handle up to 3 PSI but I never found any British car that could handle more than 1.5 PSI and that is at a high RPM.
If it is a problem you will see it go way high on even the first rev up. So you don't have to worry about it melting your hose end. When I am done I just remove the drive-in piece of brake line and put a large sheet metal screw in the pipe.
Let me know,
Howard
---------- FOLLOW-UP ----------
QUESTION: Howard,
I will check this tomorrow. However, I did check for exhaust back pressure at the tailpipe. I held the edge of a paper towel at the tailpipe. This indicated no back pressure until the engine went anemic. At that point the edge of the towel was intermittently pulled into the pipe.
What does this suggest? If the pressure test at the EGR hole shows more than 1.5 PSI, what does this indicate? What is my problem?
One other bit of info I did not previously convey ... my '74 engine has a pre-emission, early 70's cam.
Howard
ANSWER: Your tail pipe test means absolutely nothing.
If you have a high back pressure measured as I told you, it means you have a partially stopped up muffler. No engine can continue to generate vacuum if the air it took in plus combustion can't leave the house.
The 74 cam and the 70 cam both should generate vacuum on the intake stroke.
The other Howard
---------- FOLLOW-UP ----------
QUESTION: Howard,
I both checked the exhaust back pressure and pulled the muffler. Back pressure was less than 1/2 PSI and the muffler was free of any debris.
I also replaced the fuel pump ... no improvement. The next morning the engine went anemic as soon as I started it which is different from past experiences. So, I pulled both carbs. Found two problems and made a couple of changes. The problems were the front carb bowl was empty ... cause was a sliver of fuel hose that I found in the fuel line section that feeds the carbs. This is the reason for the anemic operation at start up. However, I think the sliver was generated when I changed the fuel pump and not the cause of the original problem. I also found that I had previously fitted the carb to manifold gasket incorrectly ... the bypass valve hole was covered. I corrected this.
I rechecked the float levels - 17 mm. The inlet jets were removed, checked and cleaned. They seem to function correctly. I made the following adjustments: turned the adjustment nuts on the temp compensators in 1/4 turn; adjusted the bypass valve screws to one turn after the nut was in the hex hole; I leaned each carb 1/4 turn based on spark plug appearance.
All of this has made some change to the situation. The engine now misses after the engine is hot rather than going completely anemic. What I noticed when I did the "in the garage" idle test is that when the engine is cold or warm (not hot), opening the throttle creates a smooth swoosh as the air is pulled over the bridge. After about 15 minutes when the engine is hot I get a sputtering sound when I open the throttle. During a test drive the engine ran strong until about 3 or 4 miles and then started missing or hesitating.
What do you think / suggest?
Howard
AnswerYou need to ID if the problem is fuel or ignition and you have not established that yet.
Put a timing light on the coil wire so that you have almost a steady flash. Tape the trigger down and run the wires out form under the hood and put the timing light under a wiper arm so you can view the flash of the light. It it is a bright sunny day you may have to tape a piece of cardboard
over the timing light so you can see the flash. Then drive the car until it misses and watch the flash. When you have a primary ignition miss it will show up in the flash of the light as a flicker in the normally smooth light normally seen of a coil wire.
This will at least rule out the primary of the ignition.
You should put a "T" in the fuel line just before the carbs and put a fuel pressure gauge on a long hose and run it out under the other wiper arm so you can see fuel pressure at the time of failure. This will tell if the new fuel pump is supplying pressure at the time of failure and thus eliminate fuel supply as a fault.
Did you adjust the valves and set the timing?
Howard
