Have a Stanadyne IP that overall runs great. However, when the engine is at full temp and it’s hot outside my low idle rpms will increase? Normal cold idle rpms are around 650. Even at engine full temp on a cold day these won’t go up much higher but on a hot day it will reach around 800 rpms at idle? I’ll admit it sounds weird that there’s a difference in the outside temperature I’m saying is related to this. Through research I’ve read that there could be a bimetallic strip of metal on the governor arm assembly. This is to open up the metering valve as the ambient temperature rises to compensate for the hotter thinner fuel in efforts to maintain engine rpm. That being said I do think that is what I’m seeing and it is working well. My question is, how can I adjust it to not give me to much fuel thus increasing my rpms to 800 at idle? I read a thread just a year or two back on this page and you guys sounded to have a pretty good understanding of these pumps. Any information is appreciated.
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Stanadyne IP fast idle
- Thread starter Bsikes81
- Start date
There is a other post going around here right now that shows the DB2 pump revs up right before it shuts down from lack of fuel.
Fast idle is controller by an external solenoid and temp switch on the passenger side cylinder head. Are these active or not?
Fast idle is controller by an external solenoid and temp switch on the passenger side cylinder head. Are these active or not?
Fast idle solenoid is active. It seems to be working correctly. At start up cold engine it kicks out the plunger increasing rpms slightly above 650. Then when engine reaches around 100 degrees the plunger retracts and the rpm goes back to 650. I did suspect maybe it was reactivating when hot so I unplugged it but still am getting the fast idle results at full engine temp. Plus the fast idle solenoid currently only increases rpms maybe by 75. So I don’t think it is the culprit in raising my hot engine rpms to 800.
All that being said, I do feel my throttle linkage is not right. To me it sits to far forward and sits right on the fast idle plunger. I have the low idle screw backed almost completely out. The fast idle plunger is screwed in to its solenoid very deep to where only about a 1/4 of plunger is sticking out. Overall I feel that the throttle linkage sits too far forward. However, with the exception of the fast idle when hot, the engine starts good cold, starts good hot and runs good.
Barrman
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Any idea what your IP timing is? Or, are the hash marks lined up or even close?
Actually I don’t know about the IP timing. Not familiar with the hash marks or where to find them but if you have this information I’ll check it out on mine.
Barrman
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Why, I just happen to have a video about that:
Barrman
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Here is another one describing the ways of checking the timing in more detail:
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Nice video! I seen the timing marks. Would that be similar or same on a Ford setup you think? What do you loosen to move it?
I did check mine and the timing marks were in the same location. Mine looked to be a line width towards the passenger side. I haven’t tried the governor advance trick you did in the video yet. Do you think that the overall performance of the pump can be ok but the timing being off is a factor in the increase idle rpms when engine is a full operating temp? I’ll admit sometimes under a load I will see some blue smoke out the exhaust.
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That’s really nice info! Much appreciated! I did learn through your video that my timing mark is one line width advanced.
Do you think the timing can be related to the increased idle rpms when engine is hot?
Barrman
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This is going to read as condescending. I don’t mean it that way. I just don’t know how to write it polite.
How do you know the rpm is increasing when at operating temperature? Feel, sound or actual tachometer?
If it really is increasing, then independent of a binding accessory such as a water pump, alternator, power steering pump. Or a fuel supply restriction/lift pump thing. It is probably an internal injection pump issue.
One last possible rude question. What year and model vehicle is this on? Your avatar is a GMT400 truck. If it is that truck you are asking about then it might be an apples and oranges thing going on here depending on the year. All of the GMT400’s have an electric lift pump and 994 to 1999 have the electronic DB4 IP. Totally different animal but since you write about the throttle cable I assume you are working on a DB2.
How do you know the rpm is increasing when at operating temperature? Feel, sound or actual tachometer?
If it really is increasing, then independent of a binding accessory such as a water pump, alternator, power steering pump. Or a fuel supply restriction/lift pump thing. It is probably an internal injection pump issue.
One last possible rude question. What year and model vehicle is this on? Your avatar is a GMT400 truck. If it is that truck you are asking about then it might be an apples and oranges thing going on here depending on the year. All of the GMT400’s have an electric lift pump and 994 to 1999 have the electronic DB4 IP. Totally different animal but since you write about the throttle cable I assume you are working on a DB2.
Not rude at all. I didn’t realize my avatar said GMT400, I’ll try to fix that.
It’s on a 93 Ford IDI.
I know the rpms increase by the tachometer. I can hear it’s elevated by sound too.
This is cold idle…
This is warm idle…
probably doesn’t seem like a big issue but it bothers me. Main reason is because when I shut the engine off, the belt chirps. I thought it was normal until one day it threw the belt off and broke the tensioner pulley when I shut the engine off. At that time I thought it was just the tensioner pulley so I replaced it. Put the belt back on and still had the chirp when shutting the engine off. A week later the belt flew off when I shut the engine off and broke the tensioner again. I replaced tensioner and a new belt this time. With the new belt no more chips when shutting off the engine. It has been several months now and the tensioner is still going. This may not make any sense but the last time I worked on the tensioner it was in November and getting cold. Through the winter months my full temperature engine idle rpms did really rise. They stayed close to 675 rpm. I do not know why the winter months would matter other than keeping the engine little cooler than in the hot summer temperatures.
I have read this in a DB2 article…
Retention of heat is a critical factor in fuel thinning after a high-ambient heat soak. As the hotter, thinner fuel passes through the pump, internal leakage increases and reduces fuel output. To compensate for this loss, a bimetallic temperature compensator strip was added to the governor arm to increase the metering valve opening. This provides a compensated idle speed curve and corrects engine idle speed at elevated ambient temperature.
I feel this is what I’m seeing and I believe it to be working I just don’t know if there is a way to adjust it?
Overall the elevated rpms at idle don’t bother except I believe it puts strain on the belt and tensioner and ultimately leads to it breaking. Along with premature belt wear.
Barrman
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You know what happens when you assume? I did that to myself. I assumed the crew cab dually in your avatar was a Chevy. Sorry.
Not a problem. Your videos on timing the IP are very informative and easy to understand.