Low Idle/Low Power, on an '89

[rowland]

Gee, the low power thing seems to be going around.



My truck just developed it's own set of issues. The last week or two I've been noticing that the idle seemed a bit low, and that putting it in drive drug the rpm's down quite a bit. Today it became obvious that something is wrong. Rather than it's usual 750-800 idle, it's now idling at around 680 rpm in Park and drags down to 580 rpm when I put it in gear. Boost is also down about 3 psi at WOT (16 vs 19), and I lost the slight black haze I usually get when I step on it. Power is way down, this is one sick truck.



It seems like it's not getting enough fuel. I tried changing the filter with no results and the lift pump pumps fine by hand and isn't leaking. Nothing wrong with the air filter either. I'm a bit worried that something is wrong with the pump just based on the way the engine drags down when I put it in gear. (I did turn the idle screw up to normal idle and it still drags down 100 rpm when I put it in drive). I'm thinking the next step is to get a fuel pressure gauge, but I'm open to suggestions.



Luckily, my wife is out of town for the week so I can use her Jeep to commute to work. I'm sidelining the truck until I figure this out just to avoid damaging anything further.



Any thoughts before I go do something expensive?



Isaac

 

[Greenleaf]

... ... ... ... . yep, low power issue. Check that lift pump pressure.

 

[rowland]

I'll see if I can come up with a gauge somewhere in town. The truck was sitting for about a year and a half prior to me firing it up about two months ago. One other possible option I thought of is that accumulated gunk and sludge could possibly have clogged the pick up in the tank. Of course I JUST topped the tank off sunday morning... I think I can put a vac gauge on the pump inlet though, and check for that.



Isaac

 

[dpuckett]

If it has been sitting for a year, I'd say you have varnish, sludge, etc, built up and needs a refresh- disassembled, cleaned up, and a new seal kit put in.



Daniel

 

[rowland]

What part of the system needs a new seal kit?



I did treat the fuel prior to parking it, and fired it up every month or two while it was sitting. Since then I have put about 3500-4000 miles on it, mostly hauling a good load, with no problems until recently. That doesn't rule out sludge as a possible problem of course. It's going to be a royal pain if I have to get into that tank.



It does still start instantly. When I get off work I'll try to round up a fuel pressure gauge. I'm going to be suprised if the lift pump is the problem, just because it pumps so well by hand. It would be a nice suprise though. Cheap and easy compared to some of the other possibilities.



Isaac

 

[dpuckett]

I was referring to the pump, but if you had started it and ran it, that should be ok, unless the fuel started to break down?.



Be sure to put it under a load when you check fuel pressure- LP on my 92 would read 7psi at idle, and suck down to 6 when I revved it up in the driveway. Get out in traffic, and it'd zero out halfway through 2nd gear.



-DP

 

[rowland]

Well, I tried the easy thing....

Changing the lift pump did nothing for me. After visiting four parts stores, a performance shop, and a hardware store I think I have all the pieces to built a fuel pressure gauge. I'm planning on drilling out and taping the banjo bolt for the line tomorrow (unless somebody has a better idea). That should at least tell me which way to chase this thing. Neither direction seems like it's going to be much fun though...



Isaac

 

[Greenleaf]

I'm planning on drilling out and taping the banjo bolt for the line tomorrow (unless somebody has a better idea). That should at least tell me which way to chase this thing.



You can do this just about as easy as buying a taped banjo. Either way. Genoes Garage has 'em so will a Bosch pump shop.



Hint; The banjo bolt is advertised for use on the 24 valve engines Getcha a package or three of them banjo bolt seals. Two per bolt

 

[Niki]

I'm planning on drilling out and taping the banjo bolt for the line tomorrow (unless somebody has a better idea). That should at least tell me which way to chase this thing.



You can do this just about as easy as buying a taped banjo. Either way. Genoes Garage has 'em so will a Bosch pump shop.



Hint; The banjo bolt is advertised for use on the 24 valve engines Getcha a package or three of them banjo bolt seals. Two per bolt

Do you know the bosch part #? And who makes a good guage, doesn't there have to be something special about the guage so it doesn't break from the pulsating fuel?

 

[ARhine]

I have read you can put a needle valve inline to "snub" the pulses of the pump.



I just put a guage on temporary for testing and then removed it and put a plug in. Had a nice Lisle (sp?) guage for testing psi and vaccum on a carbed gasser. Marked in 1 psi increments up to 14psi.

 

[rowland]

That pre-tapped banjo looks pretty slick. However, seeing as how I'm on the edge of nowhere and need to get this figured out... . I drilled and tapped the one I had for 3/8" NPT and hooked the gauge up that way. The "good" news is that I have 4 psi at idle and 5. 5 psi at WOT. Obviously the supply to the pump is fine. So I guess that means the VE is shorting me fuel.



Any ideas on what I can check before I pull this thing off and have it rebuilt? I don't think a sticking guide pin would cause low idle, but I'm not an expert on these things. Is it possible for the fuel solenoid to get stuck part way open? nahh. . that can't be it. This isn't good at all, especially since the jeep I'm driving now is due to get a new radiator (thats sitting in the garage), but I can't take both vehicles down at once.



Any little old ladies out there feel they are just making too much power and want to trade pumps? Guaranteed not too cause excessive smoke... .



Otherwise, I guess I'm soliciting suggestions on where to have this thing overhauled. I'm in Alaska, so unless there is a bosch shop in Fairbanks that has been hiding from me, I'm going to have to ship it out.



Isaac

 

[Greenleaf]

I have yet to see the diaphragm lift pump pulsate a mechanical gauge. You can purchase the expensive autometer mechanical FP gauge or simply pick up a generic "made in China" low pressure gauge @ NAPA or Farm store.



My 90 has a mechanical Autometer FP gauge (0 to16 psi) and no snubber. The 92 truck has the Westach electrical 0 to 16 psi.



There is no Bosch (modified) banjo part number. The injection pump stores most likely purchase them from the same co. that Genos does and then adds 60% markup



Made by; RL Torresdal Co.



geno's part number is simply BF-Tapped. cost - $7. 00



Local injection pump shop is $18. 00

 

[rowland]

Well, before I yanked the pump and shelled out the cash, I thought I should at least check to see if I had a sticky pin. I had initially ruled that out, figuring that it wouldn't be the cause of a slow idle. However, when I did pull the top off my pump and cycled the throttle, it does appear to be stuck fast. Interestingly, the "witness" marks look like I haven't been getting full travel for a long time. My stock marks (I turned it to full fuel several years ago) both start lower and end higher on the cone Certainly I'm getting nowhere near the the deepest part of the cone. Well, I'll try to free it up and see if that fixes the problem. Hopefully the pin not moving isn't indicative of some other issue.



Isaac

 

[rowland]

Well shoot...



I worked the snot out of the AFC pin and lubed it good. It was popping out fairly easily by the time I was done. Anyhow, I put it back together and now I can barely crack 12 psi and wasn't sure I was going to make it up the hill to my house. Guess that didn't work.



I also pulled the shut off solenoid in case that was sticking, but that's not it either.



So, for you pump experts out there... . Any chance that the governer spring is broken? It's an idea I got from some old threads that involved broken springs.



I'm just wondering if there is something that I could manage to pull apart and replace myself. I'll probably end up sending it out, but thought I would check. I just built a shiny new work bench and haven't taken anything apart on it yet...



Isaac

 

[bgilbert]

Well I think you took care of the guide pin, which troubleshoots the low power. But like you said, shouldn't affect the idle. Before sending anything off or pulling anything, how about turning up the fuel screw a turn. See if that solves anything. Technically it will raise idle a bit and give more power.



Then if that helps, dump a 32 oz bottle of injector cleaner/cetane boost/additive in the tank. You might have some gummed up parts in your fuel system.

 

[Greenleaf]

My 90 would top out at 45 MPH. I rotated the throttle lever one hash mark to pull AGAINST the gov spring and installed a new lift pump. It would travel about 80MPH... ... ... .....



I then installed a new gov spring/removed the reverse lever (operates the afc)and turned up the pump. Now, when traveling at 80 mph and I drop the hammer, it will take off and set you back into the seat.



GL

 

[rowland]

I took the top off today to take a look inside. Nothing visibly wrong, no metal shavings and the governer springs are in fine shape. (btw, stock spring on an '89 is the 386). Guess the problem is deeper in the pump. I'll order a new one on Monday.



The question I have is... does anybody know how easy to update to the later intercooled type pump? I think my now intercooled truck would be happier that way since the combination of IC type head and injectors with the old non-IC pump has never been all that great for me. I'm hoping it's a straight bolt up but thought someone might know for sure. Specifically, I seem to recall that the injector lines were slightly different diameters between the old non-IC and the IC models.



Thanks,



Isaac

 

[rowland]

Ok, I think I answered my own questions. The newer pump will work with minor tweaks to the injector line hook ups and a new KSB sensor.



Isaac

 

[Greenleaf]

It's pretty durn easy to do. The KSB is one among the 32 items we simply don't need on these trucks and the injector lines can be changed or the delivery valve holders swapped. piece of cake.

 

[rowland]

Well, as it happens I had a hard time exchanging the one pump type for the other. I just ordered a stock non-IC pump from Industrial Injection and will try to get it tuned and timed to work with what I have. I would have liked to have had the updated pump, but it wasn't that big of an issue.



KSB is something I need... notice where I live? The one I have hasn't worked for for the last several years and I certainly noticed the difference.



Isaac