rough running till warm

SD diesels were widely available in the US in the 1981-86 Datsun/Nissan 720 pickups, and in Canada through '87 in the D21 pickup.

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rough running till warm


Post by fisherman »

hi i have a 1987 sd25 pickup from canada that i have had for 4 years i have driven this truck every year from seattle to cordova ak and back every year . i am writing this from cordova. any way my problem is when its cool or cold out when i start it it runs real rough and wont go above an idle smokes bad some time it takes 15 min to get up to temp and then i can get the rpms up and away i go once its warm it runs great no smoke . i thought it was a stiky inj put in some rebuilt ones runs better than ever but still wont go untill hot then i thought maybe it was air issue but that seems ok now im wondering if maybe its the fuel shut off on the injector pump sticking? any one had this problem thanks john
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Post by sidevalve »

I had a similar experience a few ago with an sd22. Changed both fuel filters. Then cleaned my fuel tank and blew out the lines. Bleed everything and problem solved. I checked my gp's at the time too but they weren't my problem. good luck to you. Keep us posted of your results. Would like to hear how you make out.
!987 toyota 2wd pick-up with a SD22 from a 82 720.
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Post by plenzen »

I am suspecting the CSD device on the fuel pump.
You are getting air in the system
Try the primer pump on the firewall over the filters
Is it spongy or is it rock hard ?
If it's spongy then you are getting air in the system somehow. Check all the clamps for the fuel lines and check them for cracks.
I have seen fuel lines with cracks in them that will suck air in but not leak fuel out.
Try the lever on CSD and see if you are able to move it. You may need a small screw driver through the two holes at the end of it to make the lever move.
When the engine is warm check the CSD where the coolant lines go into it and see that it's warm/hot/engine temp. That is where the wax pellet gets melted to retard your timing from cold start up.

I am still thinking air. As Sidevalve stated check the filter for plugged. If it's getting dirty it will create vacuum from the lift pump working so hard and when the truck sits overnight, if one of the fuel lines is cracked or leaking, it sucks air into the system.

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Post by asavage »

Paul's on the right track. The '87 SD25 has the distributor IP (Bosch VE-style), so symptoms do vary from the SD22s.

If you're running real petrodiesel (not SVO/WVO, and not biodiesel), I would do a current draw test on the GPs first, just to rule them out. Although, even with one or two out, it will hit on all four within two minutes.

The VE-style IP can have lift pump wear that can give a symptom similar to this, but it usually doen't get better when it warms up, and power would be lacking. You can't fix the worn lift pump by using an inline electric pump; the IP has to be rebuilt, period.

You can temporarily splice in a section of clear vinyl tubing on the return line from the IP to the filter head (or to the tank, if it's routed that way) and when it's running rough, see if there are air bubbles in the return line. That particular problem is very common on the IH (Ford) 6.9l V8 engines, due to leaks on the little 3mm bleed hoses between the injectors.
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.
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rough running till warm


Post by fisherman »

hi guys just got in from a comm. fishing trip. just read your posts leaving again tomorrow i hope to look at the truck next week end. i will keep you posted thanks for the info john
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rough running till warm


Post by fisherman »

hi back from fishing came in early bad weather. i am to old to be out in the gulf takeing a beating . any way was looking over some old posts on the csd [nice photo asavage] lots of info still trying to under stand how it all works .went out and started the truck. hasent been started in a couple weeks. any way fired right up no smoke.found the csd and manualy lifted it and the rpms came up. shouldnt it already be in that pos. cold ? this thing cant idle if you dont get the rpms up right away it wont get above an idle till hot. when i held up the csd with one hand and opened the throttle with the other hand the rpms would go up some then go no more and drop back an idle ? is the csd something that can be delt with in place or would i need to pull the pump? if so i probably should just have it rebuilt?. what about hooking a choke cable to it. have a few other issues but this is the one thats driving me nuts! [ my wife thinks i am nuts for buying this truck] oh and the fuel lines all look good no sign of air. some one mentioned the ford 6.9 i have one or whats left of it after 20 years of driveing the alcan a few years ago i retired it to cordova just for sommer use. last winter they had record snowfall and the wharehouse i store it in colapsed on my baby. its sitting there with a big steel beam across the hood.looks like it went in the crusher. the only straight things the tail gate. probably be another year before they git it dug out.any way sorry for rambling john
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