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When I turn the key to the run position my fuel pumps don't come on but when the key is in the start postion they do and the car starts and runs fine if the engine is cold. But if the engine is warmed up it starts hard. I belive these to be two separate problems but I am unsure. Thanks for the help.
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Hi there,
In '77 the fuel pumps are gated by airflow. A switch on the airflow sensor. So you need to crank to get vacuum to lift the airflow plate before fuel is pumped again.
The electronic relays Bob and Michael are talking about came in '78.
Hard warm starts could be a failure of the check valve or accumulator or a leaky injector, causing vapor lock, but also could be mixture being rich because of a clogged warmup regulator, aka Control Pressure Regulator. Both causes require a pressure gauge diagnosis.
--
Art Benstein near Baltimore
Only Irish coffee provides in a single glass all four essential food groups: alcohol, caffeine, sugar, and fat. - Alex Levine
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Are you saying my car shouldn't have a fuel pump relay, or that just my fuel pumps dont come on in the run position because they need vacuum?
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Thanks Art! So is it likley that I have a wiring issue(bad connection/ground)related to the airflow meter? And could this be related to my hard warm starts? It has actually got to the point were I have to let the car sit for 4+ hours before it will start again. At first it would take 10-15 seconds of cranking and now it wont start at all if the engine is warmed up. Though today I drained the battery trying to start the car so I hooked it up to a high amp battery charger and cranked it and it started after 10 seconds.
I took the relays out, took the covers off, and cleaned the contacts. They look fine, I even left the covers off so I could watch them engage before I put them back together. I also went through the fuel system from the filter back including the accumulator and everything seems fine except I believe the fuel pump is louder than it should be. Thanks again.
Greg
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Hi Greg,
From your original post in this thread:
When I turn the key to the run position my fuel pumps don't come on...
This is to be expected - not a problem
but when the key is in the start postion they do and the car starts and runs fine if the engine is cold.
Cold start is not a problem, so electric control of pumps is OK, right?
But if the engine is warmed up it starts hard.
More likely a fuel delivery or mixture problem, not a wiring problem. right?
The noisy pump is a subjective observation, but can result from not being fed enough fuel. You said you went over the fuel system. How's the delivery volume? Do you have any service literature?
--
Art Benstein near Baltimore
"Freedom is not worth having if it does not include the freedom to make mistakes."
-Mahatma Gandhi
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I only have the Haynes manual which is sometimes helpful.
I hooked up a tach today and noticed that the idle speed was staying up at 1200rpm even though the engine is warm. I am way more experienced with carbureted cars(the 240 is the only fuel injected car I own), should a fuel injected car idle down after it warms up? I went ahead and adjusted it back to 900rpm which I believe is factory. Again Thank you.
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Hi Greg,
Haynes is probably the best there is that year. Lots of additional stuff on kjet.org for converting our carb-tuned heads to continuous fuel injection.
Trying to determine where you are in ownership, I found this previous thread.
240 Starts hard when engine is warm
It worries me there's no follow up on the 7 volts at the relay question. I'm pretty much a method troubleshooter, so I'll spend $70 on a test gauge quicker than $70 on an accumulator. Sounds like you've already acquired a multimeter, so can you set me at ease about having only 7 volts on your fp relay? Does it start out at 12 but fall to 7 while cranking?
I have 4 different Haynes: 78, 81, 88, and 94, designated by the latest copyright listing on page 1 or 2. Are you working from one of them?
--
Art Benstein near Baltimore
Used to be: Everyday more money is printed for Monopoly than the US Treasury.
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I believe my book is the 94' version and I have been working from it as best I can. I just went out and tested my my fuel pump relay voltage again and I got in the 8 volt range(my bat. may have been low from cranking before). Now the wire is blue and yellow and it comes from the fuse box(is this right?)and at the fuse box I am getting over 12 volts after the fuse.
This is the first major machanical problem I have had with the car. I have done a far amount of research to try and figure this out. I for one can't afford to take the car somewhere to have it looked at and for another enjoy fixing it myself. Thanks.
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I looked over the difference between the 78 and 94 Haynes as pertains to the fuel injection. The 78 edition had a lot of good stuff the 94 threw away to cram in the later LH-jet models. Probably that editing and cramming is what gives folks a case of the dislikes toward Haynes.
The 8 volt range is low, even while cranking, when voltage is at its lowest, but could be explained by an undercharged battery. Probably it is not the reason for trouble. The blue/yellow is the starter solenoid wiring I think. Try measuring at the yellow wire coming from terminal 87 on the other relay, while the motor is running. That will appease my concerns about the low voltage you mentioned.
--
Art Benstein near Baltimore
WARNING: The consumption of alcohol may lead you to think people are laughing WITH you.
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I might have to pick one of those earlier books up, they are in the $5 range on amazon.
So I checked the yellow wire while the car was running and I got 13.2 volts so I don't think I have any electrical issues any more. I guess I could still have a full pump related problem. I replaced the fuel filter about a month ago to see if that was the problem. Last weekend I took the main pump and accumulator off they both seem fine. I could have a problem in the tank though, I can hear the in-tank pump on and it sounds normal but I haven't visually inspected it.
I am thinking that if there is a fuel delivery problem the reason it starts when it is cold is because the cold start injector still has fuel avalible from the last time it was running. Does this make sence? I am not realy sure what to try next. Thanks again.
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I am thinking that if there is a fuel delivery problem...
Well, the CS injector may get it to fire but it won't run on it once you release the key.
I am not realy sure what to try next.
I'd go back to the first suggestions you had, before we got off on this electrical tangent: Assure yourself the pumps can supply fuel volume, but doing a volume test out of the filter. That's easy. Next step is verifying residual pressure. Two ways to go here: guess and replace the accumulator, or spend what you would on that part on a pressure gauge, and know for sure. I've indicated my preference before, but keep in mind I have more than one of these cars to work on, so tool investment makes even more sense for me.
--
Art Benstein near Baltimore
She had a boyfriend with a wooden leg, but she broke it off.
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I did a volume test and I was able to fill a water bottle while cranking the motor in less than 10 seconds. Even if there is no residual pressure shouldn't the car still start if it is getting fuel up to the motor?
I can probably barrow a fuel pressure gauge and try that out this weekend.
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Good volume test!
Has the situation changed?
When I turn the key to the run position my fuel pumps don't come on but when the key is in the start postion they do and the car starts and runs fine if the engine is cold. But if the engine is warmed up it starts hard.
From your original post.
--
Art Benstein near Baltimore
He often broke into song because he couldn't find the key.
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No, I still have all the same issues.
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posted by
someone claiming to be bob
on
Sat Mar 14 21:22 CST 2009 [ RELATED]
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Fuel pump relay needs to see a pulse signal from the ignition before it will close and start the pumps. may have a leaking fuel pump check valve causing the hard hot starts.
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There are 2 types of fuel pump relays on the market. I have experienced original Volvo 1979 relay and aftermarket Scantech 2008 relay.
Both are "tachometric" relays in that they require a continual sequence of electric pulses from the low voltage side of the ignition coil in order for the relay to supply power to the fuel pump. This is a safety issue as otherwise fuel could be still pumped and spurting out and burning even though the engine has stopped in a crash.
One type of relay (Volvo original 1970s & 1980s vintage) will activate the pump for 1 second in key position II prior to start in key position III. This pressurises the fuel system and/or tops up fuel pressure as the fuel accumulator should provide some pressure if its OK. This gives a fast start with minimum cranking.
The other type (Scantech aftermarket) does not activate the pump for 1 second in key position II prior to start in key position III. It provides a 1 second pulse after it gets a pulse from the ignition coil. So if you need to pressurise the fuel system for a fast start, briefly flick the key to position III for a moment before letting it go back to position II and you will hear the pump whine as fuel system is pressurised. Then hold in position III to start.
Normally it doesnt matter what relay is used since you turn the key from position 0 rapidly to position III to start so the fuel system doesnt get any "pre-cranking pressurisation" and has to run from the reduced battery voltage while cranking. Of course if your battery and fuel accumulator are not OK then it does matter and you may need to do pre-cranking pressurisation to get a easy start.
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